Session migration (#72)

* impl

* retry logic

* simulate

* pass checks

* adjust log level

* retry condition

* fix simulate scenario params

* format

* use `RTCPeerConnectionState` instead of `RTCIceConnectionState`

* adjust retry

* additional check for completer

* more logging

* fix id

* pub

* change package

* doc update

* retry tests

* format

* apply suggestions

test/livekit_client_test.dart

@@ -1,5 +0,0 @@
-import 'package:flutter_test/flutter_test.dart';
-
-void main() {
-  test('placeholder', () {});
-}

test/utils_test.dart

@@ -0,0 +1,42 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:livekit_client/src/utils.dart';
+
+void main() {
+  group('retry', () {
+    // test if List of errors are thrown
+    test(
+      'throw all and throw error list',
+      () => expect(
+        Utils.retry<void>(
+          (triesLeft, _) => throw 'error-${triesLeft}',
+          tries: 3,
+          delay: Duration.zero,
+        ),
+        throwsA([
+          'error-2',
+          'error-1',
+          'error-0',
+        ]),
+      ),
+    );
+    test(
+      'throw once and return result',
+      () => expectLater(
+        Utils.retry<String>(
+          (triesLeft, _) async {
+            expect(
+              triesLeft,
+              isNot(0),
+              reason: 'should be never 0 because returning on 1',
+            );
+            if (triesLeft == 1) return 'result-${triesLeft}';
+            throw 'error${triesLeft}';
+          },
+          tries: 3,
+          delay: Duration.zero,
+        ),
+        completion('result-1'),
+      ),
+    );
+  });
+}