feat: Remove refresh_token grant type from automated refresh

[JorTurFer]

SA key flow is designed for machine 2 machine communication, so using refresh_token doesn't make sense from operational pov as the sessions doesn't need to be extended (like it happens for users that you want to silent refresh).

Using refresh_token grant type it's not needed because for a workload, using the jwt-bearer grant type or refresh token grant type is exactly the same, but SA's refresh_token grant type isn't OAuth compliant as it doesn't require client_id (which is mandatory).

I've tested that everything works running the backgroundrefresh example

Checklist

• No generated code was adjusted manually (check comments in file header)
• Changelogs
  • Changelog in the root directory was adjusted (see here)
  • Changelog(s) of the service(s) were adjusted (see e.g. here)
• VERSION file(s) of the service(s) were adjusted
• Code format was applied: make fmt
• Examples were added / adjusted (see examples/ directory)
• Unit tests got implemented or updated
• Unit tests are passing: make test (will be checked by CI)
• No linter issues: make lint (will be checked by CI)

[github-actions]

This PR was marked as stale after 7 days of inactivity and will be closed after another 7 days of further inactivity. If this PR should be kept open, just add a comment, remove the stale label or push new commits to it.

[JorTurFer]

Not stale

[github-actions]

This PR was marked as stale after 7 days of inactivity and will be closed after another 7 days of further inactivity. If this PR should be kept open, just add a comment, remove the stale label or push new commits to it.

[JorTurFer]

Not stale

[github-actions]

This PR was marked as stale after 7 days of inactivity and will be closed after another 7 days of further inactivity. If this PR should be kept open, just add a comment, remove the stale label or push new commits to it.