feat(useragent): initial connection impl

useragent/lib/providers/connection/connection_manager.dart

@@ -0,0 +1,39 @@
+import 'package:arbiter/features/connection/connection.dart';
+import 'package:arbiter/providers/connection/bootstrap_token.dart';
+import 'package:arbiter/providers/key.dart';
+import 'package:arbiter/providers/server_info.dart';
+import 'package:mtcore/markettakers.dart';
+import 'package:riverpod_annotation/riverpod_annotation.dart';
+
+part 'connection_manager.g.dart';
+
+@Riverpod(keepAlive: true)
+class ConnectionManager extends _$ConnectionManager {
+  @override
+  Future<Connection?> build() async {
+    final serverInfo = await ref.watch(serverInfoProvider.future);
+    final key = await ref.watch(keyProvider.future);
+    final token = ref.watch(bootstrapTokenProvider);
+
+    if (serverInfo == null || key == null) {
+      return null;
+    }
+    final Connection connection;
+    try {
+       connection = await connectAndAuthorize(serverInfo, key, bootstrapToken: token);
+    } catch (e) {
+      talker.handle(e);
+      rethrow;
+    }
+    
+
+    ref.onDispose(() {
+      final connection = state.asData?.value;
+      if (connection != null) {
+        connection.close();
+      }
+    });
+
+    return connection;
+  }
+}