feat(redirect): policies from tower-http can be used as custom policy

[linyihai]

What this PR want

Address #2576

How to implemente

Add a convert function, which can convert tower-http policy to rewqest redirect policy.

A base example could be

  use tower_http::follow_redirect::policy::{FilterCredentials, Limited};
  let _policy = Policy::custom(tower_policy(FilterCredentials::new()));

[linyihai]

Add a convert function, which can convert tower-http policy to rewqest redirect policy.

Hello, could anyone give me some feebacks? IMO, this solution is concise, and don't bring big change.

[seanmonstar]

Hey there! Thanks for working on this! I do think we could eventually consider how to make it easy to use policies from tower-http. But at the same time, publicly depending on the Policy trait means we can't upgrade tower-http freely, because that would then be a breaking change in reqwest.

The goal of the issue is kind of the opposite way around from this PR: make the internals of reqwest (so, the redirect loop inside the PendingRequest future) to use tower_http::redirect. So as to not be a breaking change to users, it'd still look like setting redirects(Policy::limit(5)), and inside we'd turn that into a tower_http::redirect::Policy. Does that make sense?

[linyihai]

Thanks your reply!

But at the same time, publicly depending on the Policy trait means we can't upgrade tower-http freely, because that would then be a breaking change in reqwest.

Oh, that's a big problem.

The goal of the issue is kind of the opposite way around from this PR: make the internals of reqwest (so, the redirect loop inside the PendingRequest future) to use tower_http::redirect. So as to not be a breaking change to users, it'd still look like setting redirects(Policy::limit(5)), and inside we'd turn that into a tower_http::redirect::Policy. Does that make sense?

Ok, I'd try this approach.