refactor(app): use jsonschema for config

[paularmstrong]

Note: looking for feedback, concerns, or agreement before I finish this up

Thinking forward to the point where we want to be able to create the config yaml from the web UI, I think it will be difficult to maintain long-term if we have more than once source of truth for what fields need to exist and how they are validated.

Switching the python application from using voluptuous to jsonschema allows for 3 key benefits:

1. We can serve the schema from the API to the web app so that it can construct forms without hardcoding any information. The forms and inputs can all be generated based on the schema. Reducing maintenance on config changes would be really nice.
2. We can build documentation straight from the schema. The current jsonschema to markdown generators that I've found don't quite output human-readable docs, so I'm going to keep looking, otherwise may write one separately, so this is a little longer out. I got a start on this and will keep updating what it looks like here.
3. Errors on startup with the config validation are more human readable. Error parsing config: 'mqtt' becomes ERROR : deque(['mqtt']) - 'host' is a required property (can probably do better, but this is a start)

There are still a few issues present that need to be fixed, like validating that rtmp and detect roles are present. Some of the more complex validation is just a little harder to write.

[blakeblackshear]

This seems like a good direction to move in. It does look like we have some conflicts in with auto-formatting that we need to sync up. If you use the vscode remote container, it should match mine.

[paularmstrong]

I can't get used to vscode. It seems you're using Black to format. I installed that and ran it and it looks like it changed a lot more formatting than previously. Do you have some extra settings set somewhere?

[paularmstrong]

Here's a start on what the output from my jsonschema-to-markdown will output. It still has a lot of things to deal with.
https://gist.github.com/paularmstrong/d2a7abf76e15bc2a4fbdc549a69fdc94

[blakeblackshear]

All the config for VSCode is here: https://github.com/blakeblackshear/frigate/blob/release-0.9.0/.devcontainer/devcontainer.json

[paularmstrong]

Looks like vscode has two things built-in with black that aren't actually on by default if you're just using black standalone (or in another IDE): --skip-string-normalization and --target-version=py36 (auto-detection default for target version seems to wind up with random results)

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[herostrat]

Is there anything I can help you with, be it coding or review?
I find this change very promising.