Isolate implementation details from application

[sergeysova]

Instead of passing body, header, path extractors to a route:

pub async fn route(
    body: web::Json<request_bodies::Register>,
    app: web::Data<crate::App>,
) -> Answer<'static, register_request::Response> {

Generate a single extractor for all data. Router implementation doesn't know about API details:

pub async fn route(
    params: paths::register_request::Params,
    app: web::Data<crate::App>,
) -> Answer<'static, register_request::Response> {