feat: add Gemini and Spartan protocol support

app/test/key_store_test.dart

@@ -0,0 +1,33 @@
+import 'dart:io';
+
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:mews/application/key_store.dart';
+
+void main() {
+  late Directory dir;
+  late KeyStore keys;
+
+  setUp(() async {
+    dir = await Directory.systemTemp.createTemp('mews-keys');
+    keys = KeyStore(() async => dir);
+  });
+
+  tearDown(() {
+    dir.deleteSync(recursive: true);
+  });
+
+  test('a key is stored, read back and removed', () async {
+    expect(await keys.read(7), isNull);
+
+    await keys.save(7, 'KEY PEM');
+    expect(await keys.read(7), 'KEY PEM');
+
+    // Saving again replaces, the way a renewed identity replaces its key.
+    await keys.save(7, 'NEW KEY PEM');
+    expect(await keys.read(7), 'NEW KEY PEM');
+
+    await keys.delete(7);
+    expect(await keys.read(7), isNull);
+  });
+}