Show deployment status on a MR view

What are the relevant issue numbers?

Resolves #19571 (closed), one in the list of #19992 (closed)

Screenshots (if relevant)

external_url = nil

external_url != nil

Note, the timings are weird between merging and deploying, that is because I did it in the wrong order.

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Tests
  • Added for this feature/bug
  • All builds are passing