feat: Opt-In for url-encoded slashes in URL paths

[dadrus]

Related issue(s)

closes #1070

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 an explicit opt-in for url-encoded slashes in URL paths, used while matching a request in all operation modes, as well as when forwarding the request to the upstream service in proxy mode.

The new rule-level configuration property is named allow_encoded_slashes and can be set to the following values:

• off - Reject requests containing encoded slashes. Means, if the request URL contains an url-encoded slash (%2F), the rule will not match it. This is also the default setting, if the property is not configured explicitly.
• on - Accept requests using encoded slashes, decoding them and making it transparent for the rules and the upstream url. That is, the %2F becomes a / and will be treated as such in all places.
• no_decode - Accept requests using encoded slashes, but not touching them and showing them to the rules and the upstream. That is, the %2F just remains as is.

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (69dd7d2) 89.16% compared to head (7cd6a7b) 89.19%.

Files	Patch %	Lines
internal/rules/rule_impl.go	95.83%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1071      +/-   ##
==========================================
+ Coverage   89.16%   89.19%   +0.03%     
==========================================
  Files         246      246              
  Lines       10305    10347      +42     
==========================================
+ Hits         9188     9229      +41     
- Misses        879      880       +1     
  Partials      238      238              

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