fix: parse all Ustrd tags

[Gared]

Currently only the first tag of Ustrd is parsed and the rest is ignored. For example if you have this payload (ING):

<RmtInf>
  <Ustrd>Beschreibung 1 un</Ustrd>
  <Ustrd>d diese geht hier weiter</Ustrd>
</RmtInf>

This change will parse all Ustrd tags