Add doc for iOS auth with SERVER_CLIENT_ID

Author: Milvintsiss

packages/google_sign_in/google_sign_in/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 5.2.3+1
+
+* Add doc for iOS auth with SERVER_CLIENT_ID
+
 ## 5.2.3
 
 * Bumps the Android dependency on `com.google.android.gms:play-services-auth` and therefore removes the need for `jetifier`.

packages/google_sign_in/google_sign_in/README.md

@@ -61,6 +61,20 @@ This plugin requires iOS 9.0 or higher.
 <!-- End of the Google Sign-in Section -->
 ```
 
+### iOS Authenticate with backend server
+
+If you use Google Sign-In with an app that communicates with a backend server,
+you might need to identify the currently signed-in user on the server.
+To check the integrity of the token on your server you need to add an extra
+`aud` field in the `idToken`.
+
+To do so you need to add a `SERVER_CLIENT_ID` key value pair in your `GoogleService-Info.plist`:
+
+```xml
+<key>SERVER_CLIENT_ID</key>
+<string>[YOUR SERVER CLIENT ID]</string>
+```
+
 #### iOS additional requirement
 
 Note that according to

packages/google_sign_in/google_sign_in/pubspec.yaml

@@ -3,7 +3,7 @@ description: Flutter plugin for Google Sign-In, a secure authentication system
   for signing in with a Google account on Android and iOS.
 repository: https://github.com/flutter/plugins/tree/main/packages/google_sign_in/google_sign_in
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+google_sign_in%22
-version: 5.2.3
+version: 5.2.3+1
 
 environment:
   sdk: ">=2.14.0 <3.0.0"