getGroupAccess function 
 
    
    
    
  Implementation
  Future<GroupAccess> getGroupAccess({
  required String chatId,
  required String did, // Decentralized Identifier
}) async {
  if (chatId.isEmpty) {
    throw Exception('chatId cannot be null or empty');
  }
  if (did.isEmpty) {
    throw Exception('did cannot be null or empty');
  }
  final user = await getUserDID(address: did);
  final result = await http.get(path: '/v1/chat/groups/$chatId/access/$user');
  if (result == null || result is String) {
    throw Exception(result ?? 'Cannot get group access for $user in $chatId');
  }
  return GroupAccess.fromJson(result);
}