feat(agents): align update validation errors

internal/handler/api/v1/agent_handler.go

@@ -149,6 +149,13 @@ func (h *AgentHandler) Update(c *gin.Context) {
 
 	agent, svcErr := h.svc.Update(c.Request.Context(), uint(id), accountID, req)
 	if svcErr != nil {
+		if errors.Is(svcErr, service.ErrAgentNameBlank) {
+			c.JSON(http.StatusUnprocessableEntity, gin.H{
+				"message":    "Name can't be blank",
+				"attributes": []string{"name"},
+			})
+			return
+		}
 		applogger.L().Errorf("Update agent %d for account %d: %v", id, accountID, svcErr)
 		handleServiceError(c, svcErr)
 		return