refac: migration crash, real-database tests, site deleted during create, ruels out of the repo, lists

internal/infrastructure/persistence/database/postgres.go

@@ -26,6 +26,7 @@ const (
 	postgresLockNotAvailable      = "55P03"
 	postgresDeadlockDetected      = "40P01"
 	postgresSerializationFailure  = "40001"
+	postgresUniqueViolation       = "23505"
 )
 
 var timeType = reflect.TypeOf(time.Time{})
@@ -115,6 +116,14 @@ func (postgresDriver) NewBackup(db *gorm.DB, directory string, now func() time.T
 var postgresContentionCodes = []string{postgresLockNotAvailable, postgresDeadlockDetected, postgresSerializationFailure}
 
 func (postgresDriver) IsLockContention(err error) bool {
+	return hasPostgresCode(err, postgresContentionCodes)
+}
+
+func (postgresDriver) IsUniqueViolation(err error) bool {
+	return hasPostgresCode(err, []string{postgresUniqueViolation})
+}
+
+func hasPostgresCode(err error, codes []string) bool {
 	var failure *pgconn.PgError
-	return errors.As(err, &failure) && slices.Contains(postgresContentionCodes, failure.Code)
+	return errors.As(err, &failure) && slices.Contains(codes, failure.Code)
 }