Docs/Comments only: Better autodevops customization documentation

See merge request gitlab-org/gitlab-ce!30247

This will make it more obvious to anyone looking to customize these
files what the source code actually is.

Update doc/user/project/merge_requests/squash_and_merge.md

See merge request gitlab-org/gitlab-ce!30103

Fix typo in updateResolvableDiscussionsCounts action

See merge request gitlab-org/gitlab-ce!30278

Use separate Prometheus metrics dirs in dev/test

Closes #63869

See merge request gitlab-org/gitlab-ce!30253

Use PostgreSQL 9.6.11 in CI tests

See merge request gitlab-org/gitlab-ce!30270

Include username in auth log

Closes #62756

See merge request gitlab-org/gitlab-ce!29821

Fetches user based on the value of 'rack.attack.match_discriminator'

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/62756

Custom username for deploy tokens

See merge request gitlab-org/gitlab-ce!29639

This new attribute is optional and used when set instead of the default
format `gitlab+deploy-token-#{id}`.

Empty usernames will be saved as null in the database.

Related to https://gitlab.com/gitlab-org/gitlab-ce/issues/50228.

Jekyll Pages template: LC_ALL=C.UTF-8

See merge request gitlab-org/gitlab-ce!29907

Start UnicornSampler in master process

Closes #63830

See merge request gitlab-org/gitlab-ce!30215

Using `on_master_start` assures that the sampler is started in
master process and not in worker processes.

Backports css class used in EE specs

Closes gitlab-ee#12534

See merge request gitlab-org/gitlab-ce!30258

Removes EE differences for app/views/groups/settings/_general.html.haml

Closes gitlab-ee#12537

See merge request gitlab-org/gitlab-ce!30257

Reconcile our team, group label definitions with our organization structure

See merge request gitlab-org/gitlab-ce!29714

Use title and description fields for issue trackers

Closes #63690

See merge request gitlab-org/gitlab-ce!30096

Cache Flipper persisted names directly to local memory storage

See merge request gitlab-org/gitlab-ce!30265

[EE] Cache Flipper persisted names directly to local memory storage

See merge request gitlab-org/gitlab-ee!14509

Port of "Use title and description fields for issue trackers"

See merge request gitlab-org/gitlab-ee!14486

Prefer offline install for yarn

See merge request gitlab-org/gitlab-ce!30267

Store Sidekiq and Web server metrics from Prometheus in separate
directories in `development` and `test` environments.

Add @pslaughter to CODEOWNERS

See merge request gitlab-org/gitlab-ce!30252