feat: client_credentials authentication strategy for Endpoint enhanced to support the same options as the corresponding finalizer

[dadrus]

Related issue(s)

relates to #959

Checklist

• I agree to follow this project's Code of Conduct.
• I have read, and I am following this repository's Contributing Guidelines.
• I have read the Security Policy.
• I have referenced an issue describing the bug/feature request.
• I have added tests that prove the correctness of my implementation.
• I have updated the documentation.

Description

This PR enhances the implementation of the available OAuth2 Client Credentials Grant flow authentication strategy for endpoint definitions and makes the same configuration options and behavior available as implemented in #956.

[codecov]

Codecov Report

Merging #971 (7c5fe03) into main (4c9f807) will increase coverage by 0.17%.
Report is 2 commits behind head on main.
The diff coverage is 91.29%.

❗ Current head 7c5fe03 differs from pull request most recent head 61efddc. Consider uploading reports for the commit 61efddc to get more accurate results

@@            Coverage Diff             @@
##             main     #971      +/-   ##
==========================================
+ Coverage   89.50%   89.68%   +0.17%     
==========================================
  Files         239      241       +2     
  Lines        9922     9946      +24     
==========================================
+ Hits         8881     8920      +39     
+ Misses        812      802      -10     
+ Partials      229      224       -5     

Files	Coverage Δ
...al/rules/endpoint/authstrategy/api_key_strategy.go	100.00% <ø> (ø)
...rules/endpoint/authstrategy/basic_auth_strategy.go	100.00% <ø> (ø)
...s/endpoint/authstrategy/token_endpoint_response.go	100.00% <100.00%> (ø)
internal/rules/endpoint/mapstructure_decoder.go	100.00% <ø> (+21.66%)	⬆️
...chanisms/authenticators/anonymous_authenticator.go	100.00% <100.00%> (ø)
...mechanisms/authenticators/generic_authenticator.go	91.59% <100.00%> (-0.28%)	⬇️
...les/mechanisms/authenticators/jwt_authenticator.go	91.95% <100.00%> (-0.19%)	⬇️
...thenticators/oauth2_introspection_authenticator.go	89.34% <100.00%> (-0.34%)	⬇️
...nal/rules/mechanisms/authorizers/cel_authorizer.go	90.00% <100.00%> (-1.31%)	⬇️
.../rules/mechanisms/authorizers/remote_authorizer.go	82.81% <100.00%> (+0.72%)	⬆️
... and 16 more

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