bring in database

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

lib/services/sync_services.dart

@@ -0,0 +1,45 @@
+import 'package:async/async.dart';
+import 'package:collection/collection.dart';
+import 'package:drift/drift.dart';
+
+import '../database/database.dart';
+import '../sources/music_source.dart';
+
+class SyncService {
+  SyncService({
+    required this.source,
+    required this.db,
+    required this.sourceId,
+  });
+
+  final MusicSource source;
+  final SubtracksDatabase db;
+  final int sourceId;
+
+  Future<void> sync() async {
+    await db.transaction(() async {
+      await syncArtists();
+    });
+  }
+
+  Future<void> syncArtists() async {
+    final sourceArtistIds = <String>{};
+
+    await for (final artists in source.allArtists().slices(200)) {
+      sourceArtistIds.addAll(artists.map((e) => e.id));
+
+      await db.batch((batch) async {
+        batch.insertAllOnConflictUpdate(
+          db.artists,
+          artists.map((artist) => artist.toDb(sourceId)),
+        );
+      });
+    }
+
+    for (var slice in sourceArtistIds.slices(kSqliteMaxVariableNumber - 1)) {
+      await db.artists.deleteWhere(
+        (tbl) => tbl.sourceId.equals(sourceId) & tbl.id.isNotIn(slice),
+      );
+    }
+  }
+}