Spike: Mermaid in OpenProject

[as-op]

Ticket

https://community.openproject.org/projects/SE/work_packages/SE-646/activity

follow up to #15118

What are you trying to achieve?

Integrate Mermaid graphs into OpenProject

• Add support in all CKeditor instances, see Spike: Mermaid plugin commonmark-ckeditor-build#133
  • WP descriptions
  • Internal Wikis
  • Activity comments
• PDF export of the description, and this is the blocker. There is no reasonable way for us to generate Mermaid diagrams on the backend.
  • Support SVG in https://github.com/opf/md-to-pdf via prawnSVG Spike: Support SVG md-to-pdf#35
  • Ruby gem https://github.com/claricle/sirena unfortunately not on par with the frontend rendering for supported graphs and the quality of those (e.g. overlapping labels) Spike: render mermaid via mmdr md-to-pdf#36
  • Rust CLI tool https://github.com/1jehuang/mermaid-rs-renderer not on par with the frontend rendering, rather hard to integrate it into our OP images
  • Mermaid CLI https://github.com/mermaid-js/mermaid-cli needs Node.js and a headless browser, a no-go for our backend, but quality the same as on the frontend
  • WASM in Ruby https://github.com/dewasm/ruby-merman adds several seconds in startup time and uses 1GB ram for even easy graphs
  • WASM in Ruby https://github.com/dewasm/ruby-pozeiden incompatible license
  • Kroki https://kroki.io/ needs either java or an additional docker deployment

Screenshots

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