Linux: Detect changes in safeStorage backend

Co-authored-by: Fedor Indutny <79877362+indutny-signal@users.noreply.github.com>

ts/types/SafeStorageBackendChangeError.ts

@@ -0,0 +1,24 @@
+// Copyright 2024 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+export class SafeStorageBackendChangeError extends Error {
+  override name = 'SafeStorageBackendChangeError';
+
+  public readonly currentBackend: string;
+  public readonly previousBackend: string;
+
+  constructor({
+    currentBackend,
+    previousBackend,
+  }: {
+    currentBackend: string;
+    previousBackend: string;
+  }) {
+    super(
+      `Detected change in safeStorage backend, can't decrypt DB key (previous: ${previousBackend}, current: ${currentBackend})`
+    );
+
+    this.currentBackend = currentBackend;
+    this.previousBackend = previousBackend;
+  }
+}