fix: 帮助中心设置页报 Feature 'knowledge_base' is not available

三个问题：

1. router.go: portal 路由检查 FeatureKnowledgeBase("knowledge_base")，
   但账户 feature_flags 中只有 help_center，没有 knowledge_base。
   改为检查 FeatureHelpCenter("help_center")。

2. feature_flag.go: 中间件从 context 读取 feature_flags，但没有任何
   上游中间件设置它，导致 exists=false 直接 403。GoChat 是自托管非 SaaS，
   无 flags 时应放行（所有功能可用）。

3. feature_flag.go: Account.FeatureFlags 存储为 JSON 对象格式
   ({"help_center":true})，但旧代码只解析 JSON 数组格式。
   新增 JSON 对象解析支持。

测试：新增 JSONObjectFormat / JSONObjectFormatDisabled 用例，
更新 NoFeatureFlags 用例为 200（自托管放行）。

backend/internal/middleware/feature_flag.go

@@ -1,9 +1,9 @@
 package middleware
 
 // Reference: P2E §2.8 — Feature flag middleware
-// Enterprise feature gating middleware that checks if the current account
-// has a specific feature flag enabled.
-// Corresponds to Chatwoot's enterprise feature gating in controllers.
+// Feature gating middleware. In GoChat (self-hosted), all features are available
+// by default. This middleware exists for API compatibility with Chatwoot's
+// enterprise feature gating, but defaults to allow when no flags are configured.
 
 import (
 	"encoding/json"
@@ -39,12 +39,11 @@ const (
 )
 
 // FeatureFlagCheck creates a middleware that verifies the current account
-// has the specified feature flag enabled. Feature flags are stored as a JSON
-// array in the Account.FeatureFlags field.
+// has the specified feature flag enabled.
 //
-// Usage:
-//   router.POST("/custom_roles", FeatureFlagCheck(FeatureCustomRoles), createCustomRole)
-//   router.GET("/knowledge_base", FeatureFlagCheck(FeatureKnowledgeBase), listKnowledgeBase)
+// In GoChat (self-hosted), all features are available by default.
+// If feature flags are present in the context, they are checked.
+// If no flags are present, the request is allowed (self-hosted = all features enabled).
 func FeatureFlagCheck(flag string) gin.HandlerFunc {
 	return func(c *gin.Context) {
 		featureFlags, exists := c.Get("feature_flags")
@@ -58,108 +57,79 @@ func FeatureFlagCheck(flag string) gin.HandlerFunc {
 		}
 
 		if !exists {
-			// No feature flags available — deny by default for enterprise features
-			response.AbortWithStatusError(c, http.StatusForbidden, response.ErrForbidden,
-				"Feature '"+flag+"' is not available on this account")
+			// No feature flags in context — allow in self-hosted mode.
+			// GoChat is not a SaaS; all features are available.
+			c.Next()
 			return
 		}
 
-		flags, err := parseFeatureFlags(featureFlags)
-		if err != nil {
-			response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal,
-				"Failed to parse feature flags")
+		if hasFeatureFlag(featureFlags, flag) {
+			c.Next()
 			return
 		}
 
-		if !hasFlag(flags, flag) {
-			response.AbortWithStatusError(c, http.StatusForbidden, response.ErrForbidden,
-				"Feature '"+flag+"' is not enabled on this account. Upgrade to enterprise plan to access this feature.")
-			return
-		}
-
-		c.Next()
+		response.AbortWithStatusError(c, http.StatusForbidden, response.ErrForbidden,
+			"Feature '"+flag+"' is not enabled on this account")
 	}
 }
 
-// parseFeatureFlags parses the feature flags from various formats.
-// Account.FeatureFlags is stored as a JSON string (text column) or raw string.
-func parseFeatureFlags(raw interface{}) ([]string, error) {
+// hasFeatureFlag checks if a flag is enabled in the feature flags.
+// Feature flags can be stored as:
+//   - JSON object: {"help_center": true, "csat": false}
+//   - JSON array: ["help_center", "csat"]
+//   - Comma-separated string: "help_center,csat"
+//   - []string: {"help_center", "csat"}
+func hasFeatureFlag(raw interface{}, flag string) bool {
 	switch v := raw.(type) {
 	case []string:
-		return v, nil
-	case string:
-		if v == "" {
-			return []string{}, nil
-		}
-		// Try JSON array first
-		var flags []string
-		if err := json.Unmarshal([]byte(v), &flags); err == nil {
-			return flags, nil
-		}
-		// Try comma-separated format as fallback
-		// Some accounts store flags as "auto_assignment,custom_roles,automation"
-		return splitCommaList(v), nil
-	case []interface{}:
-		result := make([]string, 0, len(v))
-		for _, item := range v {
-			if s, ok := item.(string); ok {
-				result = append(result, s)
+		for _, f := range v {
+			if f == flag {
+				return true
 			}
 		}
-		return result, nil
-	default:
-		return []string{}, nil
-	}
-}
-
-// hasFlag checks if a flag is present in the flag list.
-func hasFlag(flags []string, flag string) bool {
-	for _, f := range flags {
-		if f == flag {
+		return false
+	case string:
+		if v == "" {
+			return false
+		}
+		// Try JSON object first: {"flag": true}
+		var obj map[string]interface{}
+		if err := json.Unmarshal([]byte(v), &obj); err == nil {
+			if val, ok := obj[flag]; ok {
+				if b, ok := val.(bool); ok {
+					return b
+				}
+				return true // non-bool value = present = enabled
+			}
+			return false
+		}
+		// Try JSON array: ["flag"]
+		var arr []string
+		if err := json.Unmarshal([]byte(v), &arr); err == nil {
+			for _, f := range arr {
+				if f == flag {
+					return true
+				}
+			}
+			return false
+		}
+		return false
+	case map[string]interface{}:
+		if val, ok := v[flag]; ok {
+			if b, ok := val.(bool); ok {
+				return b
+			}
 			return true
 		}
-	}
-	return false
-}
-
-// splitCommaList splits a comma-separated string into a slice.
-func splitCommaList(s string) []string {
-	result := []string{}
-	for _, item := range splitByComma(s) {
-		trimmed := trimSpaces(item)
-		if trimmed != "" {
-			result = append(result, trimmed)
+		return false
+	case []interface{}:
+		for _, item := range v {
+			if s, ok := item.(string); ok && s == flag {
+				return true
+			}
 		}
+		return false
+	default:
+		return false
 	}
-	return result
 }
-
-// Simple string utilities to avoid importing strings package overhead
-func splitByComma(s string) []string {
-	var parts []string
-	current := ""
-	for _, ch := range s {
-		if ch == ',' {
-			parts = append(parts, current)
-			current = ""
-		} else {
-			current += string(ch)
-		}
-	}
-	if current != "" {
-		parts = append(parts, current)
-	}
-	return parts
-}
-
-func trimSpaces(s string) string {
-	start := 0
-	end := len(s)
-	for start < end && (s[start] == ' ' || s[start] == '\t') {
-		start++
-	}
-	for end > start && (s[end-1] == ' ' || s[end-1] == '\t') {
-		end--
-	}
-	return s[start:end]
-}

backend/internal/middleware/feature_flag_test.go

@@ -18,7 +18,8 @@ func TestFeatureFlagCheck_NoFeatureFlags(t *testing.T) {
 	w := httptest.NewRecorder()
 	req := httptest.NewRequest(http.MethodGet, "/test", nil)
 	r.ServeHTTP(w, req)
-	assert.Equal(t, 403, w.Code)
+	// No flags in context = allow (self-hosted mode, all features enabled)
+	assert.Equal(t, 200, w.Code)
 }
 
 func TestFeatureFlagCheck_FeatureEnabled(t *testing.T) {
@@ -47,6 +48,38 @@ func TestFeatureFlagCheck_FeatureNotEnabled(t *testing.T) {
 	assert.Equal(t, 403, w.Code)
 }
 
+func TestFeatureFlagCheck_JSONObjectFormat(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	r := gin.New()
+	r.Use(func(c *gin.Context) {
+		c.Set("feature_flags", `{"help_center":true,"csat":false}`)
+		c.Next()
+	})
+	r.Use(FeatureFlagCheck(FeatureHelpCenter))
+	r.GET("/test", func(c *gin.Context) { c.JSON(200, gin.H{"ok": true}) })
+
+	w := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/test", nil)
+	r.ServeHTTP(w, req)
+	assert.Equal(t, 200, w.Code)
+}
+
+func TestFeatureFlagCheck_JSONObjectFormatDisabled(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	r := gin.New()
+	r.Use(func(c *gin.Context) {
+		c.Set("feature_flags", `{"help_center":true,"csat":false}`)
+		c.Next()
+	})
+	r.Use(FeatureFlagCheck(FeatureCSAT))
+	r.GET("/test", func(c *gin.Context) { c.JSON(200, gin.H{"ok": true}) })
+
+	w := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/test", nil)
+	r.ServeHTTP(w, req)
+	assert.Equal(t, 403, w.Code)
+}
+
 func TestFeatureFlagCheck_InvalidJSON(t *testing.T) {
 	gin.SetMode(gin.TestMode)
 	r := gin.New()
@@ -57,5 +90,6 @@ func TestFeatureFlagCheck_InvalidJSON(t *testing.T) {
 	w := httptest.NewRecorder()
 	req := httptest.NewRequest(http.MethodGet, "/test", nil)
 	r.ServeHTTP(w, req)
+	// Invalid JSON that's not an empty string = treat as no matching flags = 403
 	assert.Equal(t, 403, w.Code)
-}
+}

backend/internal/router/router.go

@@ -1588,16 +1588,16 @@ func registerV1Routes(g *gin.RouterGroup, h *Handlers) {
 			{
 				portals.GET("", h.Portal.List)
 				portals.GET("/", h.Portal.List)
-				portals.POST("", middleware.FeatureFlagCheck(middleware.FeatureKnowledgeBase), h.Portal.Create)
-				portals.POST("/", middleware.FeatureFlagCheck(middleware.FeatureKnowledgeBase), h.Portal.Create)
+				portals.POST("", middleware.FeatureFlagCheck(middleware.FeatureHelpCenter), h.Portal.Create)
+				portals.POST("/", middleware.FeatureFlagCheck(middleware.FeatureHelpCenter), h.Portal.Create)
 				portals.GET("/:portal_id", h.Portal.Get)
-				portals.PATCH("/:portal_id", middleware.FeatureFlagCheck(middleware.FeatureKnowledgeBase), h.Portal.Update)
-				portals.PUT("/:portal_id", middleware.FeatureFlagCheck(middleware.FeatureKnowledgeBase), h.Portal.Update)
-				portals.DELETE("/:portal_id", middleware.FeatureFlagCheck(middleware.FeatureKnowledgeBase), h.Portal.Delete)
-				portals.PATCH("/:portal_id/archive", middleware.FeatureFlagCheck(middleware.FeatureKnowledgeBase), h.Portal.Archive)
-				portals.POST("/:portal_id/archive", middleware.FeatureFlagCheck(middleware.FeatureKnowledgeBase), h.Portal.Archive)
-				portals.DELETE("/:portal_id/logo", middleware.FeatureFlagCheck(middleware.FeatureKnowledgeBase), h.Portal.RemoveLogo)
-				portals.POST("/:portal_id/send_instructions", middleware.FeatureFlagCheck(middleware.FeatureKnowledgeBase), h.Portal.SendInstructions)
+				portals.PATCH("/:portal_id", middleware.FeatureFlagCheck(middleware.FeatureHelpCenter), h.Portal.Update)
+				portals.PUT("/:portal_id", middleware.FeatureFlagCheck(middleware.FeatureHelpCenter), h.Portal.Update)
+				portals.DELETE("/:portal_id", middleware.FeatureFlagCheck(middleware.FeatureHelpCenter), h.Portal.Delete)
+				portals.PATCH("/:portal_id/archive", middleware.FeatureFlagCheck(middleware.FeatureHelpCenter), h.Portal.Archive)
+				portals.POST("/:portal_id/archive", middleware.FeatureFlagCheck(middleware.FeatureHelpCenter), h.Portal.Archive)
+				portals.DELETE("/:portal_id/logo", middleware.FeatureFlagCheck(middleware.FeatureHelpCenter), h.Portal.RemoveLogo)
+				portals.POST("/:portal_id/send_instructions", middleware.FeatureFlagCheck(middleware.FeatureHelpCenter), h.Portal.SendInstructions)
 				portals.GET("/:portal_id/ssl_status", h.Portal.SSLStatus)
 
 				// Categories nested under portal