Docs - Reorganize incoming email doc

See merge request gitlab-org/gitlab-ce!25409

Configuration examples were moved into their own section for the purpose
of organizing and being able to link directly.

Add note on configuring an external Redis Sentinel instance

See merge request gitlab-org/gitlab-ce!25436

Adding password in the Redis Sentinel config does not actually work
because v3.2.x doesn't respond to the `AUTH` command.

This came up in
https://gitlab.com/gitlab-org/omnibus-gitlab/issues/4126.

Docs: Move chatops docs from EE to core

See merge request gitlab-org/gitlab-ce!25324

ChatOps used to be in the Ultimate tier.

Docs: document upgrade k8s apps

See merge request gitlab-org/gitlab-ce!25323

Clarify that Owners have permissions to change visibility.

See merge request gitlab-org/gitlab-ce!25356

Team Member Removed: "project_access" changed to "access_level".  Team Member...

See merge request gitlab-org/gitlab-ce!25306

Move language setting to preferences

Closes #35638

See merge request gitlab-org/gitlab-ce!25427

Template and process improvements for documentation

See merge request gitlab-org/gitlab-ce!24315

Move ChatOps to Core

See merge request gitlab-org/gitlab-ce!24780

ChatOps used to be in the Ultimate tier.

fix #39010 - add left margin to 1st time contributor badge

Closes #39010

See merge request gitlab-org/gitlab-ce!25216

Document how to enable feature flags for Review Apps

See merge request gitlab-org/gitlab-ce!25399

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

Ignore revert commits

Closes #57912

See merge request gitlab-org/gitlab-ce!25396

Quarantine failing test

See merge request gitlab-org/gitlab-ce!25424

Docs: change badges.svg example to pipeline.svg

See merge request gitlab-org/gitlab-ce!25157

Added id to namespace name generator

See merge request gitlab-org/gitlab-ce!25285

Removed quarantine tag from the squash merges test;

Bump helm and kubectl for Kubernetes integration

See merge request gitlab-org/gitlab-ce!25268

This introduces additional method for linting,
to reduce the complexity of `lint_commits`.

Remove undigested token column from personal_access_tokens table

See merge request gitlab-org/gitlab-ce!22743

Token column are no longer used as token values are stored digested in
token_digest.

Update docs to indicate unicorn metrics are automatically scraped

See merge request gitlab-org/gitlab-ce!25406

Added missing comma in sample response json for list of boards and a single board

See merge request gitlab-org/gitlab-ce!25419

Update QA docs: clarify spec vs. specs/features and use end-to-end instead of integration

See merge request gitlab-org/gitlab-ce!25413

Fix WebHookService spec failing in Ruby 2.6

See merge request gitlab-org/gitlab-ce!25317

Bump Helm and kubectl in Auto DevOps

See merge request gitlab-org/gitlab-ce!25072

Comment why we can't use Gitlab::CurrentSettings

See merge request gitlab-org/gitlab-ce!25412

Upgrade Webmock to 3.5.1

See merge request gitlab-org/gitlab-ce!25318

Refactor CI/CD landing page

Closes #50498 and #56973

See merge request gitlab-org/gitlab-ce!24894

Restructures existing page and adds improvements.