The Ginger resource id. We 'tag' the resource id with type Int
using elm-tagged.
This helps us to not mix up some other Int with a resource id by accident.
The only way to construct a ResourceId is by decoding one from some json or
parsing it out of an url path. This is rather strict and there might be some times
you just need to create a random ResourceId for whatever reason, this hasn't
come up so far, but file an issue if it does.