Example gRPC broadcaster

This is an example gRPC broadcaster written with Tonic.
It takes a stream of messages, and echoes that back to
all known subscribers.

grpc/broadcaster/proto/service.proto

@@ -0,0 +1,14 @@
+// SPDX-FileCopyrightText: 2023 Matteo Settenvini <matteo.settenvini@montecristosoftware.eu>
+// SPDX-License-Identifier: CC0-1.0
+
+syntax = "proto3";
+
+package package;
+
+service Service {
+    rpc Broadcaster (stream Message) returns (stream Message);
+}
+
+message Message {
+    string contents = 1;
+}