This change introduces the new `tower-layer` crate and the foundational `Layer` trait to go along with it. This trait allows one to easily compose a set of `Service`s that take an inner service. These services only modify the request/response. This also provides the `Layer` implementation for many of the tower crates.
- Inspect the request, response, and error when determining to retry
- Return a future if retry is desired
- This future allows an impl to delay a retry
- The future yields a new `Policy`, allowing state to be changed
for later retries.
Jake Shadle
David Barsky
Carl Lerche
Lucio Franco
Sean McArthur