feat(worker): add durable background jobs

internal/model/background_job.go

@@ -0,0 +1,41 @@
+package model
+
+import (
+	"encoding/json"
+	"time"
+)
+
+const (
+	BackgroundJobStatusQueued    = "queued"
+	BackgroundJobStatusRunning   = "running"
+	BackgroundJobStatusRetrying  = "retrying"
+	BackgroundJobStatusCompleted = "completed"
+	BackgroundJobStatusDead      = "dead"
+)
+
+const DefaultBackgroundJobQueue = "default"
+
+// BackgroundJob stores durable background work in the database.
+// Reference: Chatwoot ActiveJob/Sidekiq jobs with retry, delayed scheduling,
+// mutex/idempotency, and observable failure state.
+type BackgroundJob struct {
+	ID             uint            `gorm:"primaryKey" json:"id"`
+	Queue          string          `gorm:"size:100;not null;default:'default';index:idx_background_jobs_ready,priority:2" json:"queue"`
+	JobType        string          `gorm:"size:150;not null;index" json:"job_type"`
+	Payload        json.RawMessage `gorm:"type:jsonb;not null;default:'{}'" json:"payload"`
+	Status         string          `gorm:"size:50;not null;default:'queued';index:idx_background_jobs_ready,priority:1" json:"status"`
+	Priority       int             `gorm:"not null;default:0" json:"priority"`
+	Attempts       int             `gorm:"not null;default:0" json:"attempts"`
+	MaxAttempts    int             `gorm:"not null;default:3" json:"max_attempts"`
+	ScheduledAt    time.Time       `gorm:"not null;index:idx_background_jobs_ready,priority:3" json:"scheduled_at"`
+	LockedAt       *time.Time      `gorm:"index" json:"locked_at,omitempty"`
+	LockedBy       string          `gorm:"size:150" json:"locked_by,omitempty"`
+	IdempotencyKey string          `gorm:"size:255;index" json:"idempotency_key,omitempty"`
+	LastError      string          `gorm:"type:text" json:"last_error,omitempty"`
+	FinishedAt     *time.Time      `json:"finished_at,omitempty"`
+	FailedAt       *time.Time      `json:"failed_at,omitempty"`
+	CreatedAt      time.Time       `gorm:"autoCreateTime" json:"created_at"`
+	UpdatedAt      time.Time       `gorm:"autoUpdateTime" json:"updated_at"`
+}
+
+func (BackgroundJob) TableName() string { return "background_jobs" }