* Use String#sub with RegEx instead of String#delete_prefix

* Use match instead match?
* Use String#chomp instead of String#delete_prefix

* Use match instead match?

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

The way Discord integration is implemented causes dependency problems.

* Use match instead match?

* Use match instead match?

This reverts commit 78ba7bcf.

This reverts commit 07ec2c7b.

* Use match instead match?

`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]

Add DNS rebinding protection settings

See merge request gitlab/gitlabhq!3132

This was renamed in GitLab 11.11, so the backport needs to use
the original name.