fix: update redirect logic for URLs ending with '/'

[bjohansebas]

Summary

Okay, this took me a bit of time to understand. This is something similar to what send does. After several attempts, it can probably be refactored even more, but this would be the main solution.

The send workflow is: if it detects a trailing slash at the end of pathname ("/") (line of code), then it goes into another code path, where it joins the original pathname and appends the index (line of code which is configurable, just like in this package). When they are joined, if such an index file exists, it continues with the normal workflow, otherwise, it throws an error, similar to what is handled here. The difference is that now, if there is a trailing slash, the index file (which is configurable) is also appended

What kind of change does this PR introduce?

Did you add tests for your changes?

Does this PR introduce a breaking change?

yes!

If relevant, what needs to be documented once your changes are merged or what have you already documented?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.70%. Comparing base (35dd70b) to head (ee8725d).

Additional details and impacted files

@@            Coverage Diff             @@
##             next    #2255      +/-   ##
==========================================
+ Coverage   95.67%   95.70%   +0.02%     
==========================================
  Files          13       13              
  Lines         901      907       +6     
  Branches      263      267       +4     
==========================================
+ Hits          862      868       +6     
  Misses         39       39              

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