http: Multiple arg of Cids/IpfsPath

[koivunej]

There are a few Options structs, which are basically the deserialized form the of the paths query string:

$ rg "TryFrom<&'a str> for" http/src/
http/src/v0/block/options.rs
14:impl<'a> TryFrom<&'a str> for RmOptions {

http/src/v0/pin/add.rs
55:impl<'a> TryFrom<&'a str> for AddRequest {

http/src/v0/refs/options.rs
42:impl<'a> TryFrom<&'a str> for RefsOptions {

http/src/v0/pin.rs
34:impl<'a> TryFrom<&'a str> for ListRequest {

These needed to be added because the plain serde_urlencoded at least did not support at the time deserializing for example this:

#[derive(Debug)]
pub struct AddRequest {
    arg: Vec<StringSerialized<Cid>>,
    recursive: bool,
    progress: bool,
}

This might be a limitation of serde "object model" or I just failed to use the library. Writing the TryFrom conversions seemed fast and flexible enough. If this arg: Vec<FromStr> member cannot be supported with serde_urlencoded we should probably just skip the particular field, and manually parse only the arg value. The best outcome of this would be a single custom filter for deserializing these "special" kinds of "options". Right now it would seem that each of these "special options" needs a custom filter creating method as well.

See for previous attempts: https://github.com/rs-ipfs/rust-ipfs/pull/349/files#r480903618

[koivunej]

Also very likely that this issue comes from me misunderstanding how should serde_urlencoded be used, feel free to fix in other ways as well 👍! Minimizing boilerplate and thus LOC needed per request representation (such as AddRequest above) is key.