Updates changelog, adds default gradle value (#2070)

Adds a filler gradle value for the URI scheme since without that, it will have a build time failure even if the user isn't using HostedUI.

Also updates the Changelog with the documentation users will need to migrate.

Author: TrekSoft

CHANGELOG.md

@@ -1,5 +1,21 @@
 # Change Log - AWS SDK for Android
 
+## [Release 2.18.0](https://github.com/aws/aws-sdk-android/releases/tag/release_v2.18.0)
+
+*Version 2.18.0 introduces breaking changes against 2.17.1.*
+
+### Breaking Updates
+- aws-android-sdk-mobile-client:
+   - No breaking changes code-wise but if you already setup HostedUI for an older version of the SDK,  
+   you'll need to follow the steps in the [updated documentation](https://docs.amplify.aws/sdk/auth/hosted-ui/q/platform/android#setup-amazon-cognito-hosted-ui-in-android-app)
+   to properly handle the response going forward.
+- aws-android-sdk-cognitoauth:
+   - `getSession()` method has been refactored to `getSession(Activity activity)`, where `activity` is an instance of 
+   the activity the user is calling this method from. It uses this to launch HostedUI if it needs to sign in again.
+   - `getSession(boolean launchWebUIIfExpired)` has been refactored to `getSessionWithoutWebUI()`. It will get session 
+   information if the refresh token is still valid, otherwise will throw an exception indicating the user must sign in 
+   again.
+
 ## [Release 2.17.0](https://github.com/aws/aws-sdk-android/releases/tag/release_v2.17.0)
 
 *Version 2.17.0 introduces breaking changes against 2.16.13.*

aws-android-sdk-cognitoauth/build.gradle

@@ -9,6 +9,10 @@ android {
         targetSdkVersion 29
         versionCode 1
         versionName '1.0'
+
+        manifestPlaceholders = [
+                'authRedirectScheme': 'FOR_LIBRARY_CONSUMER_TO_OVERRIDE'
+        ]
     }
 
     compileOptions {