feat: add grpc server streaming adapter

crates/crank-adapter-grpc/src/test_support.rs

@@ -1,4 +1,5 @@
 use base64::{Engine as _, engine::general_purpose::STANDARD};
+use futures_util::stream;
 use tokio::net::TcpListener;
 use tonic::{Request, Response, Status, transport::Server};
 
@@ -20,6 +21,30 @@ impl echo::echo_service_server::EchoService for EchoServiceImpl {
             message: request.into_inner().message,
         }))
     }
+
+    type ServerEchoStream = std::pin::Pin<
+        Box<dyn futures_util::Stream<Item = Result<echo::EchoResponse, Status>> + Send>,
+    >;
+
+    async fn server_echo(
+        &self,
+        request: Request<echo::EchoRequest>,
+    ) -> Result<Response<Self::ServerEchoStream>, Status> {
+        let message = request.into_inner().message;
+        let events = vec![
+            Ok(echo::EchoResponse {
+                message: format!("{message}-one"),
+            }),
+            Ok(echo::EchoResponse {
+                message: format!("{message}-two"),
+            }),
+            Ok(echo::EchoResponse {
+                message: format!("{message}-three"),
+            }),
+        ];
+
+        Ok(Response::new(Box::pin(stream::iter(events))))
+    }
 }
 
 pub async fn spawn_unary_echo_server() -> String {