[ramonskie]

Adds switchblade coverage for apps bound to a Redis session store. There is none today: the existing with_phpredis integration test binds no service, so the sessions extension never runs its Compile phase.

What the test does

• Deploys fixtures/with_sessions with a user-provided service named redis-sessions (WithServices).
• Asserts staging succeeds and the logs contain the extension Compile phase with no compilation failure.
• Asserts the runtime php.ini directives the extension rewrites are visible: session.save_handler=redis, session.name=PHPSESSIONID.

The fixture only reads ini_get() values and never starts a session, so no Redis server is required.

Why it fails right now

NewPHPConfigHelper resolves php.ini/php-fpm.conf from ctx.BuildDir, which is empty at staging. It opens the relative path php/etc/php.ini, so the app fails with:

Extension compilation failed: extension sessions compile failed: failed to load PHP config: failed to load php.ini: failed to read config file php/etc/php.ini: no such file or directory

Fix is in #1313. This PR is expected to be red until that lands; it is the regression guard for it. Rebase/re-run after #1313 merges, no changes to the test should be needed.

Notes

• CI runs the integration suite on the docker platform, where WithServices turns each entry into a user-provided VCAP_SERVICES entry named <app>-<key>. The redis-sessions key is what triggers SessionsExtension.ShouldCompile.
• Adds one app push per integration matrix entry.