AuthFromMD is a helper function for extracting the :authorization header from the gRPC metadata of the request.

StreamServerInterceptor returns a new unary server interceptors that performs per-request auth.

UnaryServerInterceptor returns a new unary server interceptors that performs per-request auth.

ServiceAuthFuncOverride allows a given gRPC service implementation to override the global `AuthFunc`.

AuthFunc is the pluggable function that performs authentication.