Description of problem:
Opening a WebUI page with a repository, "Backend Identifier" is always empty. There should be pulp repository UUID instead - it is sometimes valuable for debugging.


Version-Release number of selected component (if applicable):
Sat 6.6.1


How reproducible:
100%


Steps to Reproduce:
1. Enable or create some repo.
2. In WebUI, click to the repo details (via Content -> Products -> some product -> some its repo)
3. Check "Backend Identifier"


Actual results:
3. empty identifier


Expected results:
3. Should be UUID of pulp repository


Additional info:
Trivial fix:

https://github.com/Katello/katello/blob/master/app/views/katello/api/v2/repositories/base.json.rabl#L5 needs to remove the "=> :backend_identifier" bits