Run startup css as-if-foss if startup css has changed

• Feedback issue
• Full context MR (permanent draft)
• Update startup css which fixes login pages
• Add generate:startup_css yarn script
  • Add startup-css-check in CI (depends on parent MR)
• Fix startup-css-check as-if-foss rules
• Run startup css as-if-foss if startup css has changed

What does this MR do?

EDIT: This MR updates the default-frontend-jobs-as-if-foss to rule, to run if there are any startup CSS changes. This will prevent broken FOSS builds since both CE/EE startup CSS files will need to be checked and updated.

Why not just always run the starutp-css-check as-if-foss job?

The startup-css-check job depends on the frontend fixtures, so the jobs need to share the same rules. We do not want the as-if-foss jobs to always run, so we compromise and add this conditional run.

Original

This MR adds a Dangerfile to ensure that [RUN AS-IF-FOSS] is added to the MR if the startup CSS files are changed.

Thanks

Thanks so much to @oregand @markrian @cwoolley-gitlab @jannik_lehmann @nfriend for hopping on the pairing session and helping put this together!

Screenshots

EDIT: Check out this MR used to test the CI rules !63371 (closed)

No startup CSS changes made	Startup CSS changes made

Original

• These screenshots were taken on this MR with pushing a commit that changed one of the startup CSS files.

Startup changes	Startup changes with [RUN AS-IF-FOSS]