Fix sporadic test failures

[mugiwaraluffy56]

Change(s)

Change Type: Fixed

Change Category: Internal

Changelog Entry: Fix sporadic test failures

tests were randomly failing (~2 out of 9 runs), found two issues:

• logged_in_user() was missing try/finally so if a test failed inside the
  with block, keycloak_openid.introspect never got restored and the mock
  leaked into the next tests (403 instead of 401, mocked requests not firing, etc.)

• some timestamp comparisons used < instead of <=, on a fast machine the
  timestamps can be equal so the assertion fails

How to Test

run pytest src/tests a few times and check the failures from #688 don't show up

Checklist

• Tests have been added or updated to reflect the changes, or their absence is explicitly explained.
• Documentation has been added or updated to reflect the changes, or their absence is explicitly explained.
• A self review has been conducted checking:
  • No unintended changes have been committed.
  • The changes in isolation seem reasonable.
  • Anything that may be odd or unintuitive is provided with a GitHub comment.
• All CI checks pass before pinging a reviewer, or provide an explanation if they do not.
• The PR title matches the changelog entry's one line description.

Related Issues

Closes #688