Docs/submission diagram update

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Describe the pull request:

• [x] Code cleanup
• [x] Build system change
• [x] Documentation change

Changes made:

• make use of mermaid diagrams to update database schema, submission workflow, GA4GH visas workflow
• introduce mermaid diagram rendering
• remove some outdated css and outdated sequence submission workflow diagram
• update data out to be data retrieval (to have a consistent language)

Related issues:

Additional information:

• Diagrams are not that visible on a small screen, and i tried looking for zooming options, but failed short there

Release note:

Documentation change:

Mentions:

@aaperis apologies about taking the task related to db, but i found this: https://github.com/KarnerTh/mermerd that helped me generate the diagram. Still feel free to make changes

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we could split the diagrams or try to find a way to zoom into them

I know at least on github there is a way to zoom

for now merging,