Add default scopes based on provider

[jkroepke]

What this PR does / why we need it

Which issue this PR fixes

(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #

• fixes #

Special notes for your reviewer

Particularly user-facing changes

Checklist

Complete these before marking the PR as ready to review:

• DCO signed
• The PR title has a summary of the changes
• The PR body has a summary to reflect any significant (and particularly user-facing) changes introduced by this PR

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (9385d1d) 77.85% compared to head (39d7184) 77.34%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #58      +/-   ##
==========================================
- Coverage   77.85%   77.34%   -0.51%     
==========================================
  Files          20       20              
  Lines        1314     1320       +6     
==========================================
- Hits         1023     1021       -2     
- Misses        240      246       +6     
- Partials       51       53       +2     

Files	Coverage Δ
internal/config/config.go	96.19% <100.00%> (ø)
internal/oauth2/provider.go	79.81% <100.00%> (+0.76%)	⬆️
internal/oauth2/providers/generic/main.go	50.00% <0.00%> (-16.67%)	⬇️

... and 2 files with indirect coverage changes

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