Publish or update the group announcement

await OpenIM.iMManager.groupManager.setGroupInfo(
  GroupInfo(
    groupID: groupID,
    notification: announcement.trim(),
  ),
);

notification is the group announcement and is different from the group description in introduction. Pass an empty string to clear the announcement. OpenIMServer performs the final permission check.

Future completion, arrival of onGroupInfoChanged, and a reconciliation query are three separate stages.