anchor.diff:  err_recipient_unavailable() ->
       err(wait, 'recipient-unavailable', 404).
   
  --spec err_recipient_unavailable(binary(), binary()) -> stanza_error().
  +-spec err_recipient_unavailable(reason_text(), lang()) -> stanza_error().
   err_recipient_unavailable(Text, Lang) ->
       err(wait, 'recipient-unavailable', 404, Text, Lang).
   
  
positive.code: err_service_unavailable() ->
      err(cancel, 'service-unavailable', 503).
  
  -spec err_service_unavailable(binary(), binary()) -> stanza_error().
  err_service_unavailable(Text, Lang) ->
      err(cancel, 'service-unavailable', 503, Text, Lang).
  
  
negative.code: err_registration_required() ->
      err(auth, 'registration-required', 407).
  
  -spec err_registration_required(reason_text(), lang()) -> stanza_error().
  err_registration_required(Text, Lang) ->
      err(auth, 'registration-required', 407, Text, Lang).
  
  