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]

[ci skip]

Fix private feature Elasticsearch leak

See merge request gitlab/gitlabhq!3451

Add spec to test different combinations.
Accept string for required_minimum_access_level
Allow more flexible project membership query

Fix broken specs : Generate new GPG key in place of expired one

Closes #32956

See merge request gitlab-org/gitlab!17853

[ci skip]

Fix Gitaly SearchBlobs flag RPC injection [Gitaly v1.59.3]

See merge request gitlab/gitlabhq!3434

Check that SAML identity linking validates the origin of the request

See merge request gitlab/gitlabhq!3377