bring in database

switch to just using source models (no extra db fields)
start re-implementing sync service

test/util/subsonic.dart

@@ -0,0 +1,34 @@
+import 'package:subtracks/sources/subsonic/client.dart';
+import 'package:test/test.dart';
+
+import 'http.dart';
+
+enum Servers {
+  navidrome,
+  gonic,
+}
+
+Map<Servers, SubsonicClient> testServerClients() => {
+  Servers.navidrome: SubsonicClient(
+    http: TestHttpClient(),
+    address: Uri.parse('http://localhost:4533/'),
+    username: 'admin',
+    password: 'password',
+  ),
+  Servers.gonic: SubsonicClient(
+    http: TestHttpClient(),
+    address: Uri.parse('http://localhost:4747/'),
+    username: 'admin',
+    password: 'admin',
+  ),
+};
+
+void groupByTestServer(void Function(SubsonicClient client) callback) {
+  final clients = testServerClients();
+
+  for (final MapEntry(key: server, value: client) in clients.entries) {
+    group(server.name, () {
+      callback(client);
+    });
+  }
+}