Function handle_upgrade 

pub fn handle_upgrade<T>(
    msg: T,
) -> impl Future<Output = Result<Upgraded, OpaqueError>>
where
    T: HandleUpgrade,

Gets a pending HTTP upgrade from this message and handles it.

This can be called on the following types:

• http::Request<B>
• http::Response<B>
• &rama_http::Request<B>
• &rama_http::Response<B>