Show digitization date on collections instead for titles

[acka47]

Currently the digitization date ("Erstellt") is shown on individual titles but not on collections, see e.g. this title and the collection it is part of.

This information should actually be associated with the collection and not every title that is part of it.

[acka47]

The data comes from field 533, from the source of the menioned example title:

  <marc:datafield ind1=" " ind2=" " tag="533">
    <marc:subfield code="a">Digitalisierte Ausgabe</marc:subfield>
    <marc:subfield code="b">Frankfurt a. M.</marc:subfield>
    <marc:subfield code="c">Deutsche Nationalbibliothek</marc:subfield>
    <marc:subfield code="d">1998-2003</marc:subfield>
    <marc:subfield code="f">Exilpresse digital. Deutsche Exilzeitschriften 1933-1945</marc:subfield>
  </marc:datafield>