Identification of Items and Bitstreams belonging to a certain Toolbox Text-ID

Based on the discussion between @dariok @FreundJ @tittel @sika and me. @qzhao @bkremmli fyi

The Toolbox must be able to retrieve links to single files, for example images, that it can use later. There are two possibilities for this:

• We can register the final links with the toolbox
  • Not possible when the Text-ID is registered as we don't have the DSpace handle yet
  • Could be done at a later stage
• The toolbox can retrieve the links via an API by querying for the Toolbox-ID
  • Requires the Toolbox-ID to be included in the DSpace metadata if we use the DSpace REST API