feat: jwt finalizer extended to support templating via values property

[dadrus]

Related issue(s)

closes #2137

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 implements the idea described in the referenced FR.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.49%. Comparing base (2b4e1c0) to head (3849481).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2193      +/-   ##
==========================================
+ Coverage   90.46%   90.49%   +0.02%     
==========================================
  Files         279      279              
  Lines       12230    12247      +17     
==========================================
+ Hits        11064    11083      +19     
+ Misses        921      919       -2     
  Partials      245      245              

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