feat(jupyter): send Jupyter messaging metadata with Deno.jupyter.broadcast (#20714)

Exposes
[`metadata`](https://jupyter-client.readthedocs.io/en/latest/messaging.html#metadata)
to the `Deno.jupyter.broadcast` API.

```js
await Deno.jupyter.broadcast(msgType, content, metadata);
```

The metadata is required for
[`"comm_open"`](https://github.com/jupyter-widgets/ipywidgets/blob/main/packages/schema/messages.md#instantiating-a-widget-object-1)
for with `jupyter.widget` target.

cli/js/40_jupyter.js

@@ -9,8 +9,8 @@ function enableJupyter() {
   } = core.ensureFastOps();
 
   globalThis.Deno.jupyter = {
-    async broadcast(msgType, content) {
-      await op_jupyter_broadcast(msgType, content);
+    async broadcast(msgType, content, { metadata = {} } = {}) {
+      await op_jupyter_broadcast(msgType, content, metadata);
     },
   };
 }

cli/ops/jupyter.rs

@@ -36,6 +36,7 @@ pub async fn op_jupyter_broadcast(
   state: Rc<RefCell<OpState>>,
   #[string] message_type: String,
   #[serde] content: serde_json::Value,
+  #[serde] metadata: serde_json::Value,
 ) -> Result<(), AnyError> {
   let (iopub_socket, last_execution_request) = {
     let s = state.borrow();
@@ -52,6 +53,7 @@ pub async fn op_jupyter_broadcast(
     last_request
       .new_message(&message_type)
       .with_content(content)
+      .with_metadata(metadata)
       .send(&mut *iopub_socket.lock().await)
       .await?;
   }

cli/tools/jupyter/jupyter_msg.rs

@@ -206,6 +206,14 @@ impl JupyterMessage {
     self
   }
 
+  pub(crate) fn with_metadata(
+    mut self,
+    metadata: serde_json::Value,
+  ) -> JupyterMessage {
+    self.metadata = metadata;
+    self
+  }
+
   pub(crate) async fn send<S: zeromq::SocketSend>(
     &self,
     connection: &mut Connection<S>,

cli/tsc/dts/lib.deno.unstable.d.ts

@@ -1978,6 +1978,9 @@ declare namespace Deno {
     export function broadcast(
       msgType: string,
       content: Record<string, unknown>,
+      extra?: {
+        metadata?: Record<string, unknown>;
+      },
     ): Promise<void>;
   }
 }