Fixes #38038 - Show full GPG Key URL

[sbernhard]

In case you want to manually configure repositories provided by Katello and use GPG keys for them, its helpful to have the full GPG key URL on the repositories details page so that you can copy/paste it.

What are the changes introduced in this pull request?

• Added field to have the full_gpg_key_url
• Added this field on the API
• Added this field on the UI

Considerations taken when implementing this change?

In case you want to manually configure repositories provided by Katello
and use GPG keys for them, its helpful to have the full GPG key URL on
the repositories details page so that you can copy/paste it.

What are the testing steps for this pull request?

• Check if the field is part of the API (http://192.168.121.219:3000/katello/api/repositories/9)
• Check if the field is visible on the UI and has a value on the UI if a GPG Key is available.
• The UI field on the UI should not be visible if no GPG key is set

[sbernhard]

Maybe a good candidate for you @chris1984 :)