fix: Configuration of basic_auth authenticator fixed

[dadrus]

Related issue(s)

None

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.

Description

The schema configuration for the basic_auth authenticator was not inline with the documentation and the implementation. Instead of the property user_id it has client_id defined, which is neither defined by the RFC 7617, nor implemented and documented this way. So basically, the usage of the basic_auth authenticator is impossible until this PR

[codecov]

Codecov Report

Merging #556 (b937b09) into main (dba0a87) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #556   +/-   ##
=======================================
  Coverage   88.71%   88.71%           
=======================================
  Files         207      207           
  Lines        8809     8809           
=======================================
  Hits         7815     7815           
  Misses        804      804           
  Partials      190      190           

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