to the external_url from persisted environment,
and make the other utility methods private as
we don't really need to use them outside of the job.

Also update the document and add a changelog entry

* implemented logging of project and system web hooks
* implemented UI for user area (project hooks)
* implemented UI for admin area (system hooks)
* implemented retry of logged webhook
* NOT imeplemented log remover

Enforced by the database, and no callbacks need to be called.

Combined with 7b9b2c6099 and 294a8b8a6d this resolves
gitlab-org/gitlab-ce#31799

Use the EnforcedStyleForMultiline: no_comma option.
Signed-off-by: NRémy Coutable <remy@rymai.me>

Make it gracefully handle unexisting pipelines and refactor iterating
all the merge request paths.

And add some specs.

Turn ExpirePipelineCacheService into Worker so it can fetch all the
merge requests for which the pipeline runs or did run against.

Enable caching in the Etag::Middleware and when a pipeline changes
status, expire the cache for the project pipelines path.