[wip] Make REPL URL params extensible

[bollwyvl]

References

• starts Provide IURLParamManager #503

Code changes

this is still pretty WIP, names, etc. will probably change a lot.

• adds IReplApi as an exposed service in a new plugin
  • offers some before/after events for a few points in the app lifecycle
• moves existing URL params into separate plugins
  • register with partial schema
  • dynamically update themes, kernels, etc.
  • use the schema for validation, defaults
    • it's rather hard to reason about this once pluggable, as there's no way to know when all of the plugins would be done
• tests
• add a doc test app that actually uses the schema (maybe as a notebook with iframes)
  • add some headers to jupyter lite serve to allow re-embedding self?
  • add localforage-memoryStorageDriver to allow iframes, because other drivers don't work?
  • add postMessage API to get access to schema

User-facing changes

• n/a

Backwards-incompatible changes

• n/a

Notes

• the theme plugin acts a little funny, and calls itself very early
  • some race condition between the theme and the ResponsiveToolbar leads to it collapsing at weird times (it has a 500ms debouncer that's hard to reason about)
  • the ... button that reveals the toolbar is actually really awesome, but doesn't quite do the right thing

[github-actions]

👈 Try it on ReadTheDocs

[bollwyvl]

Will probably block on this until #528 is ready, as would like to do the test app with rjsf.

[bollwyvl]

I kinda wonder if our tests fail on windows because them temp dir is too long to delete...

[bollwyvl]

The more I've been tinkering with this, the more I'm thinking:

• this should apply to more of the apps
• it should centralize even more of the URL params (e.g. room, path, etc.)
• there are some challenges with race conditions

So: maybe this should hang off IRouter

• and probably upstream, eventually

So in the near term, I might split off some of the enablers of this work which are orthogonal to the actual param API:

• the localforage-memory
• extra headers for jupyter lite serve

[jtpio]

• this should apply to more of the apps

• it should centralize even more of the URL params (e.g. room, path, etc.)

• there are some challenges with race conditions

This sounds good. It would be better for the existing parameters like room and path to also be properly specified.