Types & Mapping

[karitham]

We need to make sure all the API types are correctly fleshed out, with the correct struct tags & pointers, as to meet discord's API definitions.

owmock's types are basically there, but they're not exactly implemented in the library.

We also need to map the rest of the API, but this is a long and boring task, which can be done on the go

[karitham]

Some work has been done with 7b0ddf8 but we're far from there