WIP: Add middleware package for capturing proxy time
In order to capture the latency praefect adds to each gitaly request, we need to do the following:
- praefect receives a request and records the start time, and proxies it to gitaly
- gitaly adds a gRPC trailer containing the time spent in gitaly
- praefect intercepts the trailer when the gitaly request comes back
- praefect does a difference in total time - gitaly time
This proxytime
package contains the necessary interceptors to make this happen.
This was originally in !1655 (closed), but that MR was getting too large and unwieldy.
Edited by John Cai