fix: missing issuer regression in OIDC

[aeneasr]

Closes #3182
Closes #3040

Related issue(s)

Checklist

• I have read the contributing guidelines.
• I have referenced an issue containing the design document if my change
  introduces a new feature.
• I am following the
  contributing code guidelines.
• I have read the security policy.
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security vulnerability, I
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  the changes.
• I have added tests that prove my fix is effective or that my feature
  works.
• I have added or changed the documentation.

Further Comments

[codecov]

Codecov Report

Merging #3220 (80e3642) into master (f088ccd) will increase coverage by 0.03%.
The diff coverage is 100.00%.

❗ Current head 80e3642 differs from pull request most recent head f42d65e. Consider uploading reports for the commit f42d65e to get more accurate results

@@            Coverage Diff             @@
##           master    #3220      +/-   ##
==========================================
+ Coverage   77.89%   77.93%   +0.03%     
==========================================
  Files         319      319              
  Lines       20429    20431       +2     
==========================================
+ Hits        15914    15922       +8     
+ Misses       3315     3311       -4     
+ Partials     1200     1198       -2     

Impacted Files	Coverage Δ
selfservice/strategy/oidc/provider_netid.go	75.00% <ø> (ø)
selfservice/strategy/oidc/provider_auth0.go	72.30% <100.00%> (+0.43%)	⬆️
selfservice/strategy/oidc/provider_gitlab.go	81.81% <100.00%> (+0.33%)	⬆️

... and 2 files with indirect coverage changes

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