feat(tonic): add Interceptor trait (#713)

* Expose `Interceptor` trait.

* Revert changes to public API surface.

* Rename types, add deprecated alias for old names.

tonic-build/src/client.rs

@@ -68,7 +68,7 @@ pub fn generate<T: Service>(
 
                 pub fn with_interceptor<F>(inner: T, interceptor: F) -> #service_ident<InterceptedService<T, F>>
                 where
-                    F: FnMut(tonic::Request<()>) -> Result<tonic::Request<()>, tonic::Status>,
+                    F: tonic::service::Interceptor,
                     T: tonic::codegen::Service<
                         http::Request<tonic::body::BoxBody>,
                         Response = http::Response<<T as tonic::client::GrpcService<tonic::body::BoxBody>>::ResponseBody>

tonic-build/src/server.rs

@@ -104,7 +104,7 @@ pub fn generate<T: Service>(
 
                 pub fn with_interceptor<F>(inner: T, interceptor: F) -> InterceptedService<Self, F>
                 where
-                    F: FnMut(tonic::Request<()>) -> Result<tonic::Request<()>, tonic::Status>,
+                    F: tonic::service::Interceptor,
                 {
                     InterceptedService::new(Self::new(inner), interceptor)
                 }