feat: add copy button to diagrams

Christine Belzierequested to merge
gitlab-community/gitlab-org/gitlab:add-copy-button into master

What does this MR do and why?

Adds a "Copy to clipboard" button to PlantUML diagrams, matching the existing functionality for Mermaid diagrams.

References

Closes #409451

Screenshots or screen recordings

Before After

How to set up and validate locally

Due to Web IDE limitations, I was unable to add automated tests. Tests should verify:

  • data-diagram attribute is added to <pre> element
  • data-diagram-src contains base64-encoded source
  • js-render-diagram class is present
  • Copy button functionality works end-to-end

I'm happy to add tests with guidance on the proper approach.

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Merge request reports