fix: ret invalid cred if usr not found in login

apps/backend/internal/database/errs.go

@@ -0,0 +1,61 @@
+package database
+
+import (
+	"errors"
+
+	"github.com/uptrace/bun/driver/pgdriver"
+)
+
+// PostgreSQL SQLSTATE error codes.
+// See: https://www.postgresql.org/docs/current/errcodes-appendix.html
+const (
+	PgUniqueViolation     = "23505"
+	PgForeignKeyViolation = "23503"
+	PgNotNullViolation    = "23502"
+)
+
+// PostgreSQL protocol error field identifiers used with pgdriver.Error.Field().
+// See: https://www.postgresql.org/docs/current/protocol-error-fields.html
+//
+// Common fields:
+//   - 'C' - SQLSTATE code (e.g., "23505")
+//   - 'M' - Primary error message
+//   - 'D' - Detail message
+//   - 'H' - Hint
+//   - 's' - Schema name
+//   - 't' - Table name
+//   - 'c' - Column name
+//   - 'n' - Constraint name
+const (
+	pgFieldCode       = 'C'
+	pgFieldConstraint = 'n'
+)
+
+// IsUniqueViolation checks if the error is a PostgreSQL unique constraint violation.
+func IsUniqueViolation(err error) bool {
+	return hasPgCode(err, PgUniqueViolation)
+}
+
+// IsForeignKeyViolation checks if the error is a PostgreSQL foreign key violation.
+func IsForeignKeyViolation(err error) bool {
+	return hasPgCode(err, PgForeignKeyViolation)
+}
+
+// IsNotNullViolation checks if the error is a PostgreSQL not-null constraint violation.
+func IsNotNullViolation(err error) bool {
+	return hasPgCode(err, PgNotNullViolation)
+}
+
+// ConstraintName returns the constraint name from a PostgreSQL error, or empty string if not applicable.
+func ConstraintName(err error) string {
+	var pgErr pgdriver.Error
+	if errors.As(err, &pgErr) {
+		return pgErr.Field(pgFieldConstraint)
+	}
+	return ""
+}
+
+func hasPgCode(err error, code string) bool {
+	var pgErr pgdriver.Error
+	return errors.As(err, &pgErr) && pgErr.Field(pgFieldCode) == code
+}