[REQ][rust] Trait based implementation for reqwest

[Anakael]

Is your feature request related to a problem? Please describe.

Trait based API is much more convenient than functions-based.

Describe the solution you'd like

Introduce traits and structs for API methods in reqwest implementation as it realized in hyper implementation.

[ranger-ross]

Hello,

I am very interested in this. Would the maintainer be willing to accept a PR for this?

Given that it's a pretty big change to the public api of libraries previously generated, it should probably be its own sub-template.

[wing328]

I am very interested in this. Would the maintainer be willing to accept a PR for this?

yes please

one way is to add another library (e.g. reqwest-trait) to support this

or you can create a separate generator (e.g. RustTrailtClientCodegen)

let me know if you need any help

thanks in advance for your contribution