Implement Basic App Platform about bonsaidb

[ecton]

I was investigating adding optional HTTP support via routerify and replace the server's websockets with it. It looks like routerify is going through an update to 2.0, and it might take the ecosystem a little while to get caught up. Currently routerify-websocket introduces old tokio dependencies, which I'd prefer to avoid. I want to wait until it is updated. It appears work is underway.

Overall, I like the design of routerify's API, so I'd rather wait and adopt it than seek other solutions. So, for now I'm going to just table this project for a little while and focus on other areas.

[ecton]

Tokio has a new project that looks very tempting: https://tokio.rs/blog/2021-07-announcing-axum

It honestly feels like a better choice as I can investigate exposing the HTTP layer as a tower service? Not really sure, I need to spend time understanding how tower combines services, but it seems like this is a good direction to explore.

[ecton]

In #97, I've implemented this by extending the Backend trait with an extra method when the http feature flag is enabled (server-http for the omnibus crate). I've added an example that shows how to use this to serve requests using the Axum crate. Additionally, #95 added automatic ACME certificate acquisition.

This issue as it stands has been implemented, although we still have more a grandiose vision for the platform as a whole.