Consider implementing persistent key-value database for third-parties

[JustArchi]

Something similar to my work project, where we'll allow authenticated users to store arbitrary values under unique keys.

Api should be like GET "some-unique-key" and POST "some-unique-key" "some-value".

This will allow other services, such as ASF-ui, to permanently store its own stuff in ASF's database, potentially being able to implement stuff like JustArchiNET/ASF-ui#1428 without being on ASF's mercy on doing it properly.

The database will be shared, every consumer will be expected to prepend its unique keys with some project identifier, this way we won't have conflicts over used properties.

[JustArchi]

/cc @MrBurrBurr

[JustArchi]

Note: this is expected to be API only, plugins should implement their own configs and databases similar to STD if they expect to have a similar functionality. I do not plan on making those endpoints available to them, as the values can't make use of the glorious solutions that C# gives us, such as strong-typing the saved structure.

But this is still up to final decision, I didn't make up my mind about it yet.

[JustArchi]

^ The plugins can use the above as well, if for some reason they don't want to implement their own, strong-typed classes using already-existing SerializableFile ASF abstraction.