Description of problem:
When using bearer tokens with Satellite. The token contains an expires_at field. The expires_at field is not part of the RFC for OAuth. Rather it should be expires_in.

Version-Release number of selected component (if applicable):
6.11.0

How reproducible:
Easily

Steps to Reproduce:
1. Request a OAuth token ( We authenticate and return the token like this:
https://github.com/openstack/tripleo-common/blob/master/tripleo_common/image/image_uploader.py#L326)

2. Check contents of token:

{'token': '$2a$09$1b6453892473a467d0737uJ56J02CLEXEkOaX0pdLWgLMlg.qWDSi', 'expires_at': '2022-10-28T04:54:58.296Z', 'issued_at': '2022-10-17T23:45:09.306Z'}

3. Observe expires_at field that is not valid per the RFC for OAuth:
https://www.rfc-editor.org/rfc/rfc6749#section-4.2.2

Actual results:
'expires_at': '2022-10-28T04:54:58.296Z'

Expected results:
The response should adhere to the RFC and contain a `expires_in` field. This field indicates the number of seconds since the issued_at time.

Additional info:
Upstream issue raised as well:
https://projects.theforeman.org/issues/35690

This is impacting us with new versions of Satellite here:
https://bugzilla.redhat.com/show_bug.cgi?id=2134075