anchor.diff:                            [ {group_id, GroupId}
                             , {generation_id, Generation}
                             , {member_id, MemberId}
  +                          , {group_instance_id, ?STATIC_MEMBER_ID}
                             ]),
     SendFun =
       fun() ->
  
positive.code: 
  test_full_flow(KafkaVsn) ->
    GroupId = make_group_id(full_flow_test),
    StaticMemberID = <<>>,
    % find_coordinator (group)
    {ok, Connection} = connect_coordinator(GroupId),
    % join_group
  
negative.code: leave_group(Connection, GroupId, MemberId, KafkaVsn) ->
    Fields = #{ group_id => GroupId
              , member_id => MemberId
                %% members field since 2.3
              , members => [#{member_id => MemberId,
                              group_instance_id => ?STATIC_MEMBER_ID
                             }]
              },
    Rsp = request_sync(Connection, leave_group, Fields, KafkaVsn),
    ?assertMatch(#{error_code := no_error}, Rsp),
  