Refactor `Request` to include named `context` field

[DanGould]

Request.uri and Request.body still need to be marshaled into an http library's client. In working through the issue with a dev, I think it would be more ergonomic to just return (uri: Uri, body: Vec<u8>)

After seeing the tuple solution in practice, I think it would make more sense to name context as a field in Request and have create_pj_request return Request instead of (Request, Context). tuples are not as intuitive since they lack the documentation in the form of a name or a docstring

[jbesraa]

hey, happy to try and resolve this

is what we want as a first change to modify the request struct into a struct-tuple?

struct Request {
  pub url: Url,
  pub body: Vec<u8>
}

struct Request(pub Url, pub Vec<u8>)

[jbesraa]

started this branch:

jbesraa@5230852