anchor.diff:  
   create_redirection(Url) ->
       #{header => [{<<"location">>, Url}], cookie => update, status => 302}.
  -
  -
  
positive.code:     {ok, Body} = tts_main_dtl:render(Params),
      #{body => Body, status => 200, cookie => update}.
  
  redirect_to(user_page, _ReqMap) ->
      UserPath = ?CONFIG(ep_user),
      create_redirection(UserPath);
  
negative.code: 
  revoke_credential(#{session := Session,
                      body_qs:= #{ credential_id:=CredId}}) ->
      Result = tts:revoke_credential_for(CredId, Session),
      show_credential_revoke_result(Result, Session).
  
  show_credential_request_result({ok, Credential, Log}, Session) ->
              show_user_page(Session, Credential, Log, false);
  show_credential_request_result({error, _Reason, Log}, Session) ->
              ErrMsg = <<"failed to request credential">>,
              show_user_page(Session, false, Log, ErrMsg).
  
  show_credential_revoke_result({ok, _Result, Log}, Session) ->
              show_user_page(Session, false, Log, false);
  show_credential_revoke_result({error, _Error, Log}, Session) ->
              ErrMsg = <<"failed to revoke credential">>,
              show_user_page(Session, false, Log, ErrMsg).
  
  show_user_page(Session, Credential, Log, Error) ->
      {ok, ServiceList} = tts:get_service_list_for(Session),
  