Bug/okta OIDC configuration url fix

[nickryand]

Proposed changes

Describe the big picture of your changes here to communicate to the maintainers
why we should accept this pull request. If it fixes a bug or resolves a feature
request, be sure to link to that issue.

Types of changes

Please check the type of change your PR introduces:

• Release (new release request)
• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code style update (PEP8, lint, formatting, renaming, etc)
• Refactoring (no functional changes, no api changes)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Build related changes (build process, tests runner, etc)
• Other (please describe):

Checklist

Put an x in the boxes that apply. You can also fill these out after creating
the PR. If you're unsure about any of them, don't hesitate to ask. We're here to
help! This is simply a reminder of what we are going to look for before merging
your code.

• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works

Should fix #662 without breaking non-custom auth server configurations.

[oasys]

netbox-community/netbox#8486

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (044f3c1) 77.59% compared to head (edc34f2) 77.05%.

❗ Current head edc34f2 differs from pull request most recent head f985cb5. Consider uploading reports for the commit f985cb5 to get more accurate results

Files	Patch %	Lines
social_core/backends/okta.py	87.50%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #663      +/-   ##
==========================================
- Coverage   77.59%   77.05%   -0.55%     
==========================================
  Files         343      319      -24     
  Lines       10521     9687     -834     
  Branches      699     1037     +338     
==========================================
- Hits         8164     7464     -700     
+ Misses       2200     2071     -129     
+ Partials      157      152       -5     

Flag	Coverage Δ
unittests	77.05% <92.30%> (-0.55%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[UnityDG]

Just tested this locally and seems to work

[nijel]

Can you please rebase on current master? I have no clue why GitHub didn't execute the checks...

[nickryand]

Sorry this took so long!!

[nijel]

This decoupled usage of oidc_config variable from its definition what causes test to fail.