Update 2023-04-24: UI is the focus; the migration is a separate task

So far only a predetermined number of search results are shown. I would like support for pagination.
For this we have to do the following:

• The GUI has to be adapted. See below at UI: Paging support for fetchers #5507 (comment) for a full description.
• Introduce an interface for paginated fetchers
• Migrating the implementation of fetchers (also possible step-by-step)

If there were no concerns, I would take a look.