feat(web): Implement tower::Layer for tonic_web::Config (#1119)

Signed-off-by: slinkydeveloper <[email protected]>

tonic-web/src/layer.rs

@@ -0,0 +1,31 @@
+use super::{BoxBody, BoxError, Config, GrpcWeb};
+
+use tower_layer::Layer;
+use tower_service::Service;
+
+/// Layer implementing the grpc-web protocol.
+#[derive(Debug, Clone)]
+pub struct GrpcWebLayer {
+    _priv: (),
+}
+
+impl GrpcWebLayer {
+    /// Create a new grpc-web layer.
+    pub fn new() -> GrpcWebLayer {
+        Self { _priv: () }
+    }
+}
+
+impl<S> Layer<S> for GrpcWebLayer
+where
+    S: Service<http::Request<hyper::Body>, Response = http::Response<BoxBody>>,
+    S: Clone + Send + 'static,
+    S::Future: Send + 'static,
+    S::Error: Into<BoxError> + Send,
+{
+    type Service = GrpcWeb<S>;
+
+    fn layer(&self, inner: S) -> Self::Service {
+        Config::default().enable(inner)
+    }
+}