style(backend): improve error handling

backend/internal/infrastructure/persistence/postgres/db.go

@@ -38,7 +38,7 @@ func New(dbURL string) (*pgxpool.Pool, error) {
 func transaction(ctx context.Context, db *pgxpool.Pool, handler func(context.Context, pgx.Tx) *domain.DomainError) (domainErr *domain.DomainError) {
 	tx, err := db.Begin(ctx)
 	if err != nil {
-		domainErr = domain.NewUnexpectedError(err)
+		domainErr = domain.NewErrorUnexpected().Wrap(err)
 		return
 	}
 	domainErr = handler(ctx, tx)
@@ -48,7 +48,7 @@ func transaction(ctx context.Context, db *pgxpool.Pool, handler func(context.Con
 	}
 	err = tx.Commit(ctx)
 	if err != nil {
-		domainErr = domain.NewUnexpectedError(err)
+		domainErr = domain.NewErrorUnexpected().Wrap(err)
 	}
 	return
 }