[Telecom] Improve hold capability signal

Add some method to the ConnectionService in order to notify the
connection changed.

Test: manually test and unit test
Bug: 66949982

Change-Id: I077902474f9af70e00a383aa269e1ae6ff9230a9

telecomm/java/android/telecom/Connection.java

@@ -1683,6 +1683,8 @@ public abstract class Connection extends Conferenceable {
 
     // The internal telecom call ID associated with this connection.
     private String mTelecomCallId;
+    // The PhoneAccountHandle associated with this connection.
+    private PhoneAccountHandle mPhoneAccountHandle;
     private int mState = STATE_NEW;
     private CallAudioState mCallAudioState;
     private Uri mAddress;
@@ -3075,6 +3077,27 @@ public abstract class Connection extends Conferenceable {
         }
     }
 
+    /**
+     * Sets the {@link PhoneAccountHandle} associated with this connection.
+     *
+     * @hide
+     */
+    public void setPhoneAccountHandle(PhoneAccountHandle phoneAccountHandle) {
+        if (mPhoneAccountHandle != phoneAccountHandle) {
+            mPhoneAccountHandle = phoneAccountHandle;
+            notifyPhoneAccountChanged(phoneAccountHandle);
+        }
+    }
+
+    /**
+     * Returns the {@link PhoneAccountHandle} associated with this connection.
+     *
+     * @hide
+     */
+    public PhoneAccountHandle getPhoneAccountHandle() {
+        return mPhoneAccountHandle;
+    }
+
     /**
      * Sends an event associated with this {@code Connection} with associated event extras to the
      * {@link InCallService}.