feat: add URL fragment tests

[TimothyMakkison]

• Added fragment tests, ensuring that the fragment is always removed. ie /foo#name -> /foo
• Updated InvalidParamSubstitutionShouldThrow
• Added InvalidFragmentParamSubstitutionShouldThrow

This is to prevent future changes to Uri from breaking things. I'm looking at removing Uri and UriBuilder creation in RequestBuilderImplementation.
Out of curiosity why doesn't refit support fragments, is this intentional or an oversight?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.89%. Comparing base (6ebeda5) to head (98cc73d).
Report is 157 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1900      +/-   ##
==========================================
- Coverage   87.73%   84.89%   -2.85%     
==========================================
  Files          33       36       +3     
  Lines        2348     2502     +154     
  Branches      294      361      +67     
==========================================
+ Hits         2060     2124      +64     
- Misses        208      299      +91     
+ Partials       80       79       -1     

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