Support for announcement-only groups

protos/DeviceMessages.proto

@@ -1,3 +1,6 @@
+// Copyright 2014-2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
 package signalservice;
 
 message ProvisioningUuid {
@@ -27,4 +30,4 @@ enum ProvisioningVersion {
   INITIAL        = 0;
   TABLET_SUPPORT = 1;
   CURRENT        = 1;
-}
+}