Revert "Merge branch 'blackst0ne-add-discord-service' into 'master'"

This reverts commit ca3e9b97, reversing
changes made to 89686b90.

The way Discord integration is implemented causes dependency problems.

This reverts commit 78ba7bcf.

This reverts commit 07ec2c7b.

`DeviseMailer` did not correctly handle display names set via
`Gitlab.config.gitlab.email_display_name` if they contained spaces or
special characters. It has been adjusted to handle addresses in the same
way `BaseMailer` does.

We cannot support these features at this time and they are just
cluttering the UI.

There are only three templates and they are framework-specific. The are
removed to lower complexity of the project creation page.

2FA could be enabled but still was not usedi on sign-in.

The following formerly separate commits have been merged in:

* Adjust 'Sign in' button for GitLab's CSRF protection

  GitLab introduced CSRF protection for authentication requests in
  571ba5a7. The 'Sign in' button has been
  adjusted to send a POST request.

* Opt out of turbolinks for 'Sign in' button

This restriction does not apply to admins.

This restriction does not apply to admins.

The project variable can hold an object which is not an instance of
Project (e.g. ProjectWiki). In this case, visibility_level is not
defined.

Additionally, the prompt to set a password is no longer shown for CAS
users.

[ci skip]

Update qa/Dockerfile to be built from the project root context

See merge request gitlab-org/gitlab-ce!31533

(cherry picked from commit 4d4e88df)

6aa215aa Support X_if_ee methods for QA tests
b601cfcf Update qa/Dockerfile to be built from the project root context
9a4dcd8d Update the 'build-qa-image' job to be built from project root context

Fix pipelines not always being created after a push

Closes #66196

See merge request gitlab-org/gitlab-ce!31927

(cherry picked from commit c7d12e60)

b46b9d5e Fix pipelines not always being created after a push

Migrate cycle analytics topic to new section

See merge request gitlab-org/gitlab-ce!31827

Also fixes links to new section and refactors some existing content
for the GitLab 12.2 changes.

Fix pipelines not always being created after a push

Closes #66196

See merge request gitlab-org/gitlab-ce!31927

Update docs jira service page screenshot

Closes #64778

See merge request gitlab-org/gitlab-ce!31911

Update doc/user/project/integrations/jira.md, doc/user/project/integrations/img/jira_service_page_v12_2.png files
Deleted doc/user/project/integrations/img/jira_service_page.png