[Feature Request] Types that can be converted between types that implement Serialize/Deserialize should implement Serialize and Deserialize

[Scripter17]

Various types in Reqwest can in theory implement Serde's Serialize and Deserialize traits but don't. This can get quite annoying when trying to let users configure various parts of HTTP requests via a JSON file. It requires many uses of #[serde(with = "...")] which gets N times more complicated when having Option<T>, HashMap<K, V>, HashSet<T>, etc.

A non-exhaustive list of Reqwest types that could implement Serialize and/or Deserialize pretty easily:

• HeaderMap via converting to and from HashMap
• HeaderName via as_str and FromStr
• HeaderValue via as_str and FromStr
• redirect::Policy, due to current implementation details, can only really implement Deserialize. If it kept track of if it was created via Policy::none/Policy::limited it could implement Serialize too
• Method via as_str and FromStr
• StatusCode via as_u16, FromStr, and TryFrom<u16>
• Cookie via the wrapped type
• cookie::Jar via the wrapped type
• dns::Name via as_str and FromStr

I'll see if I can do this myself, but since I'm not used to the internals of Reqwest or pull requests it might be a bit messy

[seanmonstar]

I don't currently want to implement Serialize or Deserialize on the types. I realize most of the impls would be straightforward, but I don't want to maintain that the format would stay the same.

I think an application wanting to allowing users to provide some of those as config files should define an app-specific type and format.

[Scripter17]

If the implementation only uses public APIs then there's no maintenance to do that doesn't arise from those already existing public APIs breaking