Draft: Introduce OAuth for Web IDE

• gitlab-web-ide Spike MR
• gitlab Spike MR

What does this MR do and why?

This is the Spike MR for adding OAuth to the Web IDE. It will be broken out into smaller MR's.

• Includes db migrations for adding web_ide_oauth_application to application settings.
• Includes before_action in ide_controller to ensure the web_ide_oauth_application is initialized.
• Adds a new ide#oauth_redirect endpoint and view.

Screenshots or screen recordings

20231001_oauth_web_ide_happy

How to set up and validate locally

1. Feature.enable(:web_ide_oauth) in rails console (rails c).
2. Visit IDE for any project and notice that requests are using OAuth token.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.