chore(refactor): streamline logic for HTTPRoute configuration generation

[programmer04]

What this PR does / why we need it:

Function GenerateKongRouteFromTranslation(...) is used only for validation (the fact that it is used for both flavors for validation leads to confusion). Furthermore, code related to expression routes is used only here + in tests.

This PR renames GenerateKongExpressionRoutesFromTranslation(...) to GenerateKongExpressionRoutesFromTranslationForValidation(...) and uses it explicitly in admission validation. It removes GenerateKongRouteFromTranslation(...) and does some opportunistic refeactors cleanups. Also, it gets rid of redundant parameters, helpers, etc.

Which issue this PR fixes:

Discovered during work on

• Support named routes and propagate the route name to the Gateway #6582

Special notes for your reviewer:

Changes in that PR improve the situation but don't make it perfect. I'm proposing creating a separate issue to track the effort of unifying logic for generating actual configuration sent to Kong Gateway and configuration used only for validation for expression routes. There is test coverage, so it seems to be a safe change.

[codecov]

Codecov Report

Attention: Patch coverage is 97.50000% with 1 line in your changes missing coverage. Please review.

Project coverage is 76.8%. Comparing base (f8a7606) to head (ae04588).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/admission/validation/gateway/httproute.go	96.2%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #6741     +/-   ##
=======================================
- Coverage   77.1%   76.8%   -0.3%     
=======================================
  Files        211     211             
  Lines      25299   25349     +50     
=======================================
- Hits       19517   19491     -26     
- Misses      4773    4837     +64     
- Partials    1009    1021     +12     

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[randmonkey]

Please wait for #6711 (and further #6727 for expression based routes) that will change the translation of HTTPRoute to services.

[programmer04]

Thanks for the info @randmonkey I have stacked changes for propagating named routes (#6582), but I suppose they should be applied after your change will be merged

[pmalek]

@programmer04 There are some conflicts here to resolve after the above mentioned PRs merged. Do you still intend to merge this one?

[pmalek]

Removing from 3.4 as that has already shipped and we're most likely not going to backport this. Correct me if I'm wrong @programmer04.