feat: Migrate ApplicationType to alternative enum structure

[DafyddLlyr]

Frustratingly JSONSchema doesn't support description annotations per-enum (which is very likely what lead us to this more complex structure we currently use).

You can see in this PR enums with @description notation (PA, PP) not being pulled through into the generated schema.

For WTT, I've tried adding the descriptions as JSON within the @description block. This works and allows us to encode this information in the schema, but it's not typesafe or particularly consumer friendly. It might be a decent compromise though? Thoughts very welcome!

Update: The above is now outdated, please see #218 (comment) - I have a solution which works well, we'll go with this going forward.

[DafyddLlyr]

This method doesn't work (@description per-enum)...

[DafyddLlyr]

...but this does (JSON in @description of parent).

[jessicamcinchak]

Have been doing some reading on enums in JSON Schema this morning & definitely seems like simple enum types come with the usability trade off/limitation of no support for @description annotations - and lots of things point towards the oneOf/anyOf dict style we have now as the "best practice" alternative (trade offs of harder to parse validation errors regularly noted).

But I did find one option that I quite like - this meta:enum key that's part of jsonschema2md mentioned here https://stackoverflow.com/questions/64233370/in-json-schema-how-to-define-an-enum-with-description-of-each-elements-in-the-e

Since we know some type of improved public documentation is also on our near-roadmap here, maybe this could be a two-for-one? I suspect we'd have to globally set "additionalProperties": true to support this and extend the ts to json schema generator script ourselves to pick this up (both of which may be too large of efforts to justify!), but just wanted to flag as it feels like exactly what we want !

[DafyddLlyr]

Thanks @jessicamcinchak - that link was super helpful, and lead to me this thread which suggested a combination of anyOf and const.

Take a look at aa7f59a - this looks like the solution we're looking for? 🤞

It looks like ts-json-schema-generator will combine plain string unions, but convert named types to a list of anyOf + consts.

[jessicamcinchak]

Very happy with the latest ApplicationType changes - let's merge this then we can work through other enums 🙂