Adds `tonic::Extensions` which is a newtype around `http::Extensions`.
Request extensions can be set by interceptors with
`Request::extensions_mut` and retrieved from RPCs with
`Request::extensions`. Extensions can also be set in tower middleware
and will be carried through to the RPC.
Since response extensions cannot be set by interceptors the main use
case is to set them in RPCs and retrieve them in tower middlewares.
Figured that might be useful.
Fixes https://github.com/hyperium/tonic/issues/255
This change introduces proper gRPC interceptors that are avilable
regardless of the transport used. Each codegen service now produces an
additional method called `with_interceptor` that accepts a
`Interceptor`.
All examples have been updated to use this new style and interop has a
custom `tower::Service` middleware to echo the headers. There is also a
new `interceptor` example that shows basic usage.
BREAKING CHANGE: removed `interceptor_fn` and `intercep_headers_fn` from `transport` in favor of using `tonic::Interceptor`.
