iosAppGroupId

iOS only: the App Group id (e.g. group.com.example.wallet) whose shared container holds the credential storage DB. Set this when the wallet ships an iOS Digital Credentials provider extension (.appex): the app and the extension are separate processes that must read the SAME store, so it lives at an App-Group path both can reach. Null (default) → per-process non-backed-up storage (single-process app, Android, tests). Ignored on non-iOS platforms.