Fix false RouterPathParamsModifiedError when renaming path-versioned endpoints

[zmievsa]

When api_version_location="path", the {api_version} placeholder appears
in route paths but not in dependant.path_params — FastAPI doesn't treat it
as an endpoint param. This caused a false positive in the path param
consistency check when using .had(path=...) to rename an endpoint.

Instead of inferring the version-managed param via regex diff against the
original route path, thread api_version_parameter_name from Cadwyn
through generate_versioned_routers → _EndpointTransformer →
_apply_endpoint_had_instruction, where it is discarded from the candidate
param set before comparison.

Fixes #357

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.84%. Comparing base (5a7eea2) to head (35ef027).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #358   +/-   ##
=======================================
  Coverage   99.84%   99.84%           
=======================================
  Files          72       72           
  Lines        5645     5663   +18     
  Branches      358      359    +1     
=======================================
+ Hits         5636     5654   +18     
  Misses          9        9           

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[zmievsa-semasoftware]

Code review

Found 1 issue:

1. The new test defines an inline class RenameEndpoint(VersionChange) (line 266), but the established pattern in this file is to use the version_change() helper (used ~40 times vs ~9 inline classes). Per the code review on PR Tolerate FastAPI 0.128+ utils removal, restrict fastapi >= 0.128.6 #327: "We also (almost) never use classes for tests." This case is a simple single-instruction rename that can be expressed with version_change(endpoint("/{api_version}/new-name", ["GET"]).had(path="/{api_version}/old-name")).

cadwyn/tests/test_router_generation.py

Lines 264 to 276 in 3d02910

	app_router.include_router(sub_router, prefix="/new-name")
	class RenameEndpoint(VersionChange):
	description = "Rename /old-name to /new-name"
	instructions_to_migrate_to_previous_version = (
	endpoint("/{api_version}/new-name", ["GET"]).had(path="/{api_version}/old-name"),
	)
	versions = VersionBundle(
	Version("v2", RenameEndpoint),
	Version("v1"),
	)

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