feat(redirect): add new method for Attempt

[linyihai]

Motivation

Due to Attempt fields are all private, that dissallows producting Attempt outside.

My another PR needs a way to construct a tower-http Attempt, see seanmonstar/reqwest#2617

Solution

Add a new method and passing all the needed fileds to produce the Attempt. This way has less expansibility when adding new fields to Attempt.

[seanmonstar]

I don't think this method should be required. If the loop in reqwest (which mostly exists to handle redirects) is replaced by putting the internal hyper.call() with a svc.call(), such that svc is a the hyper client (and any other eventual layers) wrapped in a tower_http::follow_redirect::FollowRedirect, then the Attempt will be constructed automatically and passed into our impl Policy.

Does all of that make sense? Would you like me to sketch out futher what I mean?

[linyihai]

I don't think this method should be required. If the loop in reqwest (which mostly exists to handle redirects) is replaced by putting the internal hyper.call() with a svc.call(), such that svc is a the hyper client (and any other eventual layers) wrapped in a tower_http::follow_redirect::FollowRedirect, then the Attempt will be constructed automatically and passed into our impl Policy.

I'll look into tower_http::follow_redirect::FollowRedirect, thanks for you reminders.

Would you like me to sketch out futher what I mean?

Yes, It would be nice if there were more implementation details