refactor(router): remove CachingRouter

[DeepDiver1975]

Description

Removes OC\Route\CachingRouter. It caches generated URLs in the distributed memory cache, and it is slower than not caching at all: measured at 9.1% slower than plain OC\Route\Router for parameterless routes, and within a few percent either way for routes with parameters. A cache whose lookup costs more than the work it avoids is a net loss, and this one also put per-instance URL strings into a network-reachable backend.

Only four references existed: the class, its single instantiation in Server.php, and two git-ignored generated classmaps. Server.php now always returns new \OC\Route\Router($c->getLogger()).

This removes the only in-tree caller of ICacheFactory::isAvailable(). The interface method is kept — it is @since 7.0.0 public API.

Drive-by: apps/files/appinfo/routes.php:67 was the one place naming the concrete router in a docblock (@var $this \OC\Route\Router); it now says \OCP\Route\IRouter, matching every other routes file.

Reviewer notes

• Behaviour genuinely changes inside the test suite: under PHPUNIT_RUN all three cache tiers are ArrayCache (Server.php:482-488), so isAvailable() is true and the caching router was live in CI. That is why the full suite was run rather than just tests/lib/Route.
• If your local classmap is stale you may need composer dump-autoload.

Related Issue

• Fixes n/a — found while auditing distributed-cache usage for GHSA-488r-cjpq-p3vc

Motivation and Context

Deletes a cache that costs more than it saves and needlessly widens the distributed-cache surface.

How Has This Been Tested?

• test environment: PHP 8.3.32, sqlite.
• test case 1: benchmark A/B of CachingRouter vs Router — 9.1% slower without parameters, ±few % with. This is the reason for the change.
• test case 2: new testRouterIsNotCached() in tests/lib/Route/RouterTest.php asserts the class no longer exists and that the service is a plain Router. tests/lib/ServerTest.php:233 still asserts instanceof IRouter and passes.
• test case 3: full tests/lib — 7149 tests, 40221 assertions, no new failures. Run in full precisely because the caching router was live under PHPUnit, so URL memoisation really does change.
• test case 4: make test-php-style and phan clean.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Database schema changes (next release will require increase of minor version instead of patch)
• Breaking change (fix or feature that would cause existing functionality to change)
• Technical debt
• Tests only (no source changes)

Checklist:

• Code changes
• Unit tests added
• Acceptance tests added
• Documentation ticket raised: n/a
• Changelog item, see TEMPLATE

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