Remove git-hooks so app can be installed with "composer create-project" without being a git repository

Some config keys changed as well since the last update

This reverts commit 2535de6a.

While it's not stricly required by everyone it doesn't require any
extra implementation right now and is required by all frontend apps
in the future, so including it should make the initial setup easier.

It gets called during composer install which we need when deploying
without dev packages.

Disabling scripts would work, but then the symfony install commands
would be skipped too...

This mainly means the keycloak config moves to a separate bundle

The core bundle is now available on packagist

While the starter bundle gives a nice example for how to integrate an API
it makes setting up a new server harder because the user usually already
has a bundle in mind that he/she wants to add.

So remove it and instead make it easier to add bundles by improving the docs

This is now handled by the composer.json in .gitlab-ci if needed

While we directed the docker image to translate the URLs to https anyway
this can be confusing since git behaves differently in docker vs outside.

Also in the meantime we have made all repos public, so there is no auth needed
for the repos and the extra work required using https no longer applies.

The main change is that the core bundle no longer contains tugraz
specifics, so we can remove the corresponding config.

This also pins api-platform/core since the new 2.6 release has various
breaking changes we haven't worked around yet.