auth: prepare v2 release

Fixes #671

Author: kevmoo

googleapis_auth/CHANGELOG.md

@@ -1,4 +1,4 @@
-## 2.0.0-wip
+## 2.0.0
 
 - Removed deprecated `RefreshFailedException`.
 - Removed deprecated `auth.dart` library.

googleapis_auth/README.md

@@ -48,18 +48,10 @@ After the Client ID has been created, you can obtain access credentials via
 import 'package:googleapis_auth/auth_browser.dart';
 
 // Initialize the browser oauth2 flow functionality then use it to obtain credentials.
-Future<AccessCredentials> obtainCredentials() async {
-  final flow = await createImplicitBrowserFlow(
-    ClientId('....apps.googleusercontent.com'),
-    ['scope1', 'scope2'],
-  );
-
-  try {
-    return await flow.obtainAccessCredentialsViaUserConsent();
-  } finally {
-    flow.close();
-  }
-}
+Future<AccessCredentials> obtainCredentials() => requestAccessCredentials(
+  clientId: '....apps.googleusercontent.com',
+  scopes: ['scope1', 'scope2'],
+);
 ```
 
 or obtain an authenticated HTTP client via

googleapis_auth/example/example.dart

@@ -0,0 +1,7 @@
+import 'package:googleapis_auth/auth_browser.dart';
+
+// Initialize the browser oauth2 flow functionality then use it to obtain credentials.
+Future<AccessCredentials> obtainCredentials() => requestAccessCredentials(
+      clientId: '....apps.googleusercontent.com',
+      scopes: ['scope1', 'scope2'],
+    );

googleapis_auth/pubspec.yaml

@@ -1,5 +1,5 @@
 name: googleapis_auth
-version: 2.0.0-wip
+version: 2.0.0
 description: Obtain Access credentials for Google services using OAuth 2.0
 repository: https://github.com/google/googleapis.dart/tree/master/googleapis_auth