feat: More convenient Host header forwarding in proxy mode

[dadrus]

Related issue(s)

closes #2264

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

As proposed in the referenced FR, this PR adds a new boolean property, forward_host_header, to the forward_to settings. This property allows you to specify whether the client Host header should be forwarded to the upstream service. The default value is true.

You can still configure a custom Host header value using a header finalizer, which will take precedence over the forward_host_header setting.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.55%. Comparing base (0413eb9) to head (16a3767).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2265      +/-   ##
==========================================
+ Coverage   90.54%   90.55%   +0.01%     
==========================================
  Files         279      279              
  Lines       12280    12298      +18     
==========================================
+ Hits        11119    11137      +18     
  Misses        916      916              
  Partials      245      245              

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