When referencing cross-namespace labels, we append the namespace name
to the rendered label.

This MR escapes the name to prevent XSS attacks.

When we un-escape HTML text to find references in it, we should then
re-escape the whole text again, not only found matches.

Because we replace matches with milestone/label links (which contain
HTML tags we don't want to escape again), we re-escape HTML text
with placeholders instead of these links and then replace placeholders
in the escaped text.

Using the sed script from
https://gitlab.com/gitlab-org/gitlab-ce/issues/59758

Signed-off-by: NRémy Coutable <remy@rymai.me>

Updates notes-related services and rendering so this code can be
easily used for group-scoped resources (specifically Epics).

Related to gitlab-ee!5205

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Remove superfluous lib: true, type: redis, service: true, models: true, services: true, no_db: true, api: true
Signed-off-by: NRémy Coutable <remy@rymai.me>

This reverts commit e00fb2bdc2090e9cabeb1eb35a2672a882cc96e9.

# Conflicts:
#	.rubocop.yml
#	.rubocop_todo.yml
#	lib/gitlab/ci/config/entry/global.rb
#	lib/gitlab/ci/config/entry/jobs.rb
#	spec/lib/gitlab/ci/config/entry/factory_spec.rb
#	spec/lib/gitlab/ci/config/entry/global_spec.rb
#	spec/lib/gitlab/ci/config/entry/job_spec.rb
#	spec/lib/gitlab/ci/status/build/factory_spec.rb
#	spec/lib/gitlab/incoming_email_spec.rb

This reverts commit cb10b725c8929b8b4460f89c9d96c773af39ba6b.

This reverts commit 96bef54154e669f9a3e92c3a4bc76c0be3a52e48.

This reverts commit 3e991230.

# Conflicts:
#	app/models/project.rb

This splits the Markdown rendering and reference extraction phases into
two distinct code bases. The reference extraction phase no longer relies
on the html-pipeline Gem (and any related code) and allows for
extracting of references from multiple HTML nodes in a single pass. This
means that if you want to extract user references from 200 comments you
no longer need to run 200 times N number of queries, instead only a
handful of queries may be needed.

Closes #15168