Reapply "feat(loyalty): EnakPoint & EnakCoin" (#32)

This reverts commit 4e24f9bbb0.

internal/repository/tx_manager.go

@@ -50,3 +50,10 @@ func (m *TxManager) WithTransactionOptions(ctx context.Context, opts *sql.TxOpti
 		return fn(ctxTx)
 	}, opts)
 }
+
+// DetachTransaction returns ctx without the caller's transaction, so work started from
+// it (such as loyalty earning after a payment) reads committed data and commits on its
+// own, whatever happens to the caller's transaction.
+func DetachTransaction(ctx context.Context) context.Context {
+	return context.WithValue(ctx, txKey, (*gorm.DB)(nil))
+}