Correct media_types API

[ry]

Fix #4292

cc @kitsonk

[kitsonk]

The purpose of the API is to normalise content-types, when users take shortcuts. See how this API is used in oak:

https://github.com/oakserver/oak/blob/99dfcda9d590b73a449e1258c7c0c2e4ab790b45/response.ts#L33-L40

So I would prefer to not make this change. Clearing up documentation of its purpose, or changing the name of the API to normalizeContentType would be better. The reason it resolves "extensions" is so that a user can set the content type to a response to something like "json" but end up with a full valid media type as output. It was never designed to do paths, as that feature is lookup().

[ry]

Actually, now that I'm looking more deeply into this library, I'm not happy with it. I want to delete it from std. In file_server, the only place it's used, we can just use a small map of filename extensions.

[kitsonk]

Again, personally, I don't care. I originally ported it to oak because it was the easiest way to replicate functionality, but I always thought it was a bit overkill for a standard library, but people kept trying to build a whole express/koa type framework in standard, and this was an easy move to help stem that need.

[ry]

OK then I'm going to remove media_types. I think it's better to kick this out into deno.land/x rather than support it forever #4594