refactor!: Configuration settings for services exposed by heimdall simplified

[dadrus]

Related issue(s)

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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 refactors heimdall’s serve configuration to improve clarity and eliminate redundancy. Currently, the configuration under the serve property contains separate settings for proxy and decision operation modes, which are mutually exclusive but largely similar. Additionally, settings for management service are included under the same serve property, while settings for other services, such as metrics and profiling, are not.

The current structure looks like this:

serve:
  proxy:
    port: 4455
    # other proxy settings

  decision:
    port: 4456
    # other decision settings

  management:
    port: 4457
    # other management service settings

metrics:
  # metrics related settings

# ...

This configuration feels unnecessarily complex, as proxy and decision modes share many settings but are configured separately. Moreover, management and other services aren’t grouped logically, making the structure harder to follow.

To address these issues, this PR simplifies the configuration by merging the proxy and decision settings directly under the serve property and moving the management settings to the top level. The new structure is as follows:

serve:
  port: 4455
  # other unified settings

management:
  port: 4457
  # other management service settings

# other settings as they were before this PR

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.37%. Comparing base (c579122) to head (3e9e2b9).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2089      +/-   ##
==========================================
- Coverage   89.45%   89.37%   -0.09%     
==========================================
  Files         271      272       +1     
  Lines       11487    11474      -13     
==========================================
- Hits        10276    10255      -21     
- Misses        970      975       +5     
- Partials      241      244       +3     

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