update architecture diagram

[jeanetteclark]

It would be nice to have a slightly more readable and editable architecture diagram, particularly as we start to think about how to implement horizontal scaling with data checks.

PlantUML within an .rst doc was suggested, this is what the new metacat diagrams are drawn in

[mbjones]

If you want to stick with Markdown, another option might be to use the new Mermaid support from GitHub. I tried it a few months ago and there were some rough edges, but seemed like it was close. Maybe worth another try.

• GitHub blog about support: https://github.blog/2022-02-14-include-diagrams-markdown-files-mermaid/
• Mermaid docs: https://mermaid-js.github.io/mermaid/#/flowchart

A simple example:

graph TD;
      A-->B;
      A-->C;
      B-->D;
      C-->D;

[jeanetteclark]

new diagrams are all in the docs