[experiment] add alternative wasm sqlite3 implementation available via build-tag (#2863)

This allows for building GoToSocial with [SQLite transpiled to WASM](https://github.com/ncruces/go-sqlite3) and accessed through [Wazero](https://wazero.io/).

internal/db/postgres/errors.go

@@ -0,0 +1,46 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package postgres
+
+import (
+	"fmt"
+
+	"github.com/jackc/pgx/v5/pgconn"
+	"github.com/superseriousbusiness/gotosocial/internal/db"
+)
+
+// processPostgresError processes an error, replacing any
+// postgres specific errors with our own error type
+func processPostgresError(err error) error {
+	// Attempt to cast as postgres
+	pgErr, ok := err.(*pgconn.PgError)
+	if !ok {
+		return err
+	}
+
+	// Handle supplied error code:
+	// (https://www.postgresql.org/docs/10/errcodes-appendix.html)
+	switch pgErr.Code { //nolint
+	case "23505" /* unique_violation */ :
+		return db.ErrAlreadyExists
+	}
+
+	// Wrap the returned error with the code and
+	// extended code for easier debugging later.
+	return fmt.Errorf("%w (code=%s)", err, pgErr.Code)
+}