Fix incompatibility between String and CommunicationUserIdentifier when serialization [1.0.0-beta.6] (#605)

* Fix incompatibility between String and CommunicationUserIdentifier when serialization

* version number update on root folder

* Remove the test app

* Fix link in README.md
Add one example to README.md

* Update CHANGELOG.md

Co-authored-by: Marc Ma <marcma@microsoft.com>

Author: marche0133

README.md

@@ -26,7 +26,7 @@ The following libraries are currently in **beta**:
 
 #### Azure Communication Services
 - [azure-communication-calling](https://search.maven.org/artifact/com.azure.android/azure-communication-calling): 1.0.0-beta.2
-- [azure-communication-chat](https://github.com/Azure/azure-sdk-for-android/blob/master/sdk/communication/azure-communication-chat): 1.0.0-beta.5
+- [azure-communication-chat](https://github.com/Azure/azure-sdk-for-android/blob/master/sdk/communication/azure-communication-chat): 1.0.0-beta.6
 - [azure-communication-common](https://github.com/Azure/azure-sdk-for-android/blob/master/sdk/communication/azure-communication-common): 1.0.0-beta.5
 
 > Note: The SDK is currently in **beta**. The API surface and feature sets are subject to change at any time before they become generally available. We do not currently recommend them for production use.
@@ -45,13 +45,13 @@ For each library you wish to use, add an `implementation` configuration to the `
 // build.gradle
 dependencies {
     ...
-    implementation "com.azure.android:azure-communication-chat:1.0.0-beta.5"
+    implementation "com.azure.android:azure-communication-chat:1.0.0-beta.6"
 }
 
 // build.gradle.kts
 dependencies {
     ...
-    implementation("com.azure.android:azure-communication-chat:1.0.0-beta.5")
+    implementation("com.azure.android:azure-communication-chat:1.0.0-beta.6")
 }
 ```
 
@@ -62,7 +62,7 @@ To import one or more client libraries into your project using the [Maven](https
 <dependency>
   <groupId>com.azure.android</groupId>
   <artifactId>azure-communication-chat</artifactId>
-  <version>1.0.0-beta.5</version>
+  <version>1.0.0-beta.6</version>
 </dependency>
 ```
 

sdk/communication/azure-communication-chat/CHANGELOG.md

@@ -1,6 +1,12 @@
 # Release History
 
-## 1.0.0-beta.6 (Unreleased)
+## 1.0.0-beta.6 (2021-02-26)
+### Breaking Changes
+- Change ChatParticipant id type from CommunicationUserIdentifier to String
+- Change ChatThread createdBy type from CommunicationUserIdentifier to String
+- Change ChatMessage senderId type from CommunicationUserIdentifier to String
+- Change ChatMessageContent initiator type from CommunicationUserIdentifier to String
+- Change ChangeMessageReadReceipt senderId type from CommunicationUserIdentifier to String
 
 ## 1.0.0-beta.5 (2021-02-08)
 ### Added