anchor.diff:  
   create_redirection(Url) ->
       #{header => [{<<"location">>, Url}], cookie => update, status => 302}.
  -
  -
  
positive.code: 
  revoke_credential(#{session := Session,
                      body_qs:= #{ credential_id:=CredId}}) ->
      case tts:revoke_credential_for(CredId, Session) of
          {ok, _Result, Log} ->
              show_user_page(Session, false, Log, false);
          {error, _Error, Log} ->
              ErrMsg = <<"failed to revoke credential">>,
              show_user_page(Session, false, Log, ErrMsg)
      end.
  
  show_user_page(Session, Credential, Log, Error) ->
      {ok, ServiceList} = tts:get_service_list_for(Session),
  
negative.code: request_credential(#{session := Session,
                       body_qs:= #{ service_id:=ServiceId}}) ->
      Iface = <<"web interface">>,
      Result = tts:request_credential_for(ServiceId, Session, [], Iface),
      show_credential_request_result(Result, Session);
  request_credential(#{session := Session}) ->
      Error = <<"Credential Request failed">>,
      show_user_page(Session, false, [], Error).
  