Add editable sign-in 'order'

Release notes

The GitLab sign-in page can now be modified to have a 'preferred' sign-in method, while leaving other forms of authentication available at the bottom of the page.

Problem to solve

A Large Self-Managed Customer has reported interest in this ticket for a way in which they can prefer a method of sign-in when multiple authentication options are available. Some end-users without proper training or guidance may use the 'first available' sign-in method without considering that a better option is available. Additionally, when multiple authentication methods are used for a migration period, different logins may be available, but one preferred over the other.

Intended users

Personas are described at https://handbook.gitlab.com/handbook/product/personas/

• Sidney (Systems Administrator)

Proposal

For the customer example specifically, they want to:

• Preference the SAML SSO button as the 'primary' or main sign-in.
• Have Standard or alternate forms of sign-in available, but not as high a priority

The customer created some examples of the intention:

Before (current state)	After (intended state)

This could be done via configuration set in the gitlab.rb file, such as:

gitlab_signin_order = ['saml_sso', 'activedirectory', 'standard']

Available Tier

Free, Premium and Ultimate