turn OptionsConfiguration to a typedef

dart/example/main.dart

@@ -18,7 +18,7 @@ Future<void> main(List<String> rawArgs) async {
   }
 
   final dsn = rawArgs.single;
-  Sentry.init(Options(dsn: dsn));
+  Sentry.init((options) => options.dsn = dsn);
 
   print('\nReporting a complete event example: ');
 
@@ -64,14 +64,3 @@ Future<void> bar() async {
 Future<void> baz() async {
   throw StateError('This is a test error');
 }
-
-class Options implements OptionsConfiguration<SentryOptions> {
-  final String dsn;
-
-  Options({this.dsn});
-
-  @override
-  void configure(SentryOptions options) {
-    options.dsn = dsn;
-  }
-}

dart/lib/src/sentry.dart

@@ -6,16 +6,19 @@ import 'client.dart';
 import 'protocol.dart';
 import 'sentry_options.dart';
 
+/// Configuration options callback
+typedef OptionsConfiguration = void Function(SentryOptions);
+
 /// Sentry SDK main entry point
 ///
 class Sentry {
   static SentryClient _client;
 
   Sentry._();
 
-  static void init(OptionsConfiguration<SentryOptions> optionsConfiguration) {
+  static void init(OptionsConfiguration optionsConfiguration) {
     final options = SentryOptions();
-    optionsConfiguration.configure(options);
+    optionsConfiguration(options);
     _client = SentryClient(
       dsn: options.dsn,
       environment: options.environment,
@@ -49,9 +52,3 @@ class Sentry {
   @visibleForTesting
   static void initClient(SentryClient client) => _client = client;
 }
-
-/// Configuration options callback
-abstract class OptionsConfiguration<T extends SentryOptions> {
-  ///configure the options
-  void configure(T options);
-}

dart/test/sentry_test.dart

@@ -1,8 +1,5 @@
 import 'package:mockito/mockito.dart';
-import 'package:sentry/src/client.dart';
-import 'package:sentry/src/protocol.dart';
-import 'package:sentry/src/sentry.dart';
-import 'package:sentry/src/sentry_options.dart';
+import 'package:sentry/sentry.dart';
 import 'package:test/test.dart';
 
 void main() {
@@ -14,7 +11,7 @@ void main() {
     final dns = 'https://[email protected]/1234567';
 
     setUp(() {
-      Sentry.init(Options(dsn: dns));
+      Sentry.init((options) => options.dsn = dns);
 
       client = MockSentryClient();
       Sentry.initClient(client);
@@ -39,17 +36,6 @@ void main() {
 
 class MockSentryClient extends Mock implements SentryClient {}
 
-class Options implements OptionsConfiguration<SentryOptions> {
-  final String dsn;
-
-  Options({this.dsn});
-
-  @override
-  void configure(SentryOptions options) {
-    options.dsn = dsn;
-  }
-}
-
 final event = Event(
   loggerName: 'main',
   serverName: 'server.dart',