Add XML conversion to bodies

[ySnoopyDogy]

The new XML validation functions just convert the data to JSON before validating the schema. With that we can just convert the data on Request and Response validations just by looking at the content type.

The XML conversion have some peculiarities, like a password field of "123456" being converted into an integer and failing validation, and the boolean conversions failing because of string fields. Because of that, I let the option to enable XML conversion default to false. If the user does not explicit enables the XML Validation, the validation is ignored just like today.

Using the option to validate XML bodies inside the Request/Response validation, we can benefit the schema compilation code.

No breaking changes with the new code

[codecov]

Codecov Report

❌ Patch coverage is 96.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 97.55%. Comparing base (cadff75) to head (1d1f518).

Files with missing lines	Patch %	Lines
responses/validate_body.go	95.12%	2 Missing ⚠️
requests/validate_body.go	96.42%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #214      +/-   ##
==========================================
- Coverage   97.58%   97.55%   -0.04%     
==========================================
  Files          56       56              
  Lines        5176     5235      +59     
==========================================
+ Hits         5051     5107      +56     
- Misses        125      128       +3     

Flag	Coverage Δ
unittests	97.55% <96.00%> (-0.04%)	⬇️

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