feat: use issuer url instead of well known url

[ZohebShaikh]

No description provided.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.03%. Comparing base (e2fd3f0) to head (e0245e3).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1371      +/-   ##
==========================================
- Coverage   95.03%   95.03%   -0.01%     
==========================================
  Files          43       43              
  Lines        2782     2779       -3     
==========================================
- Hits         2644     2641       -3     
  Misses        138      138              

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[tpoliaw]

I like this change - it makes the auth config much clearer, thanks.

That said, this is a breaking change that will need every beamline to update its config and for GDA to support the new API. We have a list of breaking issues that are waiting for a 2.0 release so it might be worth adding an issue there for this change and keeping this PR around until we decide to break everything at once.