feat(oidc): authz server issuer identification

[james-d-elliott]

This implements RFC9207 OAuth 2.0 Authorization Server Issuer Identification which is part of the FAPI 2.0 security profile.

[authelia]

Artifacts

These changes are published for testing on Buildkite, DockerHub and GitHub Container Registry.

Docker Container

• docker pull authelia/authelia:feat-oidc-rfc9207
• docker pull ghcr.io/authelia/authelia:feat-oidc-rfc9207

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[codecov]

Codecov Report

Merging #5912 (3c04cb2) into master (34b7a47) will decrease coverage by 0.01%.
The diff coverage is 59.44%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5912      +/-   ##
==========================================
- Coverage   73.52%   73.51%   -0.01%     
==========================================
  Files         281      282       +1     
  Lines       24056    24191     +135     
  Branches      443      443              
==========================================
+ Hits        17686    17784      +98     
- Misses       5629     5663      +34     
- Partials      741      744       +3     

Flag	Coverage Δ
backend	74.67% <59.44%> (-0.02%)	⬇️
frontend	58.21% <ø> (ø)

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

Files Changed	Coverage Δ
internal/middlewares/util.go	100.00% <ø> (ø)
internal/oidc/client_credentials.go	88.35% <ø> (ø)
internal/oidc/flow_client_credentials.go	100.00% <ø> (ø)
internal/oidc/flow_refresh.go	84.21% <ø> (ø)
internal/oidc/types.go	100.00% <ø> (ø)
internal/oidc/resposne_mode.go	52.58% <52.58%> (ø)
internal/handlers/handler_oidc_authorization.go	24.39% <66.66%> (+0.93%)	⬆️
internal/oidc/util.go	98.40% <90.00%> (-0.48%)	⬇️
internal/oidc/client_policy.go	39.34% <100.00%> (ø)
internal/oidc/config.go	100.00% <100.00%> (ø)
... and 1 more

... and 2 files with indirect coverage changes