add purchasing in analytics endpoint

internal/repository/tx_manager.go

@@ -28,6 +28,10 @@ func NewTxManager(db *gorm.DB) *TxManager { return &TxManager{db: db} }
 
 // WithTransaction runs fn inside a DB transaction, injecting the *gorm.DB tx into ctx.
 func (m *TxManager) WithTransaction(ctx context.Context, fn func(ctx context.Context) error) error {
+	if m == nil || m.db == nil {
+		return fn(ctx)
+	}
+
 	return m.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
 		ctxTx := context.WithValue(ctx, txKey, tx)
 		return fn(ctxTx)