TF-3157 Update web socket with background service worker

TF-3157 Stub BroadcastChannel for mobile build

web/web-sockets-worker.js

@@ -0,0 +1,74 @@
+importScripts('flutter_service_worker.js?v={{flutter_service_worker_version}}');
+
+var webSocket;
+const broadcast = new BroadcastChannel("background-message");
+var intervalId;
+const pingIntervalInMs = 10000;
+
+function connect(url, ticket) {
+  webSocket = new WebSocket(`${url}?ticket=${ticket}`, "jmap");
+
+  webSocket.onopen = () => {
+    console.log("websocket open");
+    webSocket.send(
+      JSON.stringify({
+        "@type": "WebSocketPushEnable",
+        dataTypes: ["Mailbox", "Email"],
+      })
+    );
+    intervalId = setInterval(() => {
+      webSocket.send(
+        JSON.stringify({
+          "@type": "Request",
+          id: "R1",
+          using: ["urn:ietf:params:jmap:core"],
+          methodCalls: [["Core/echo", {}, "c0"]],
+        })
+      );
+    }, pingIntervalInMs);
+  };
+
+  webSocket.onmessage = (event) => {
+    console.log(`websocket received message: ${event.data}`);
+    broadcast.postMessage(event.data);
+  };
+
+  webSocket.onclose = (event) => {
+    console.log(
+      `websocket connection closed with code: "${event.code}" reason: "${event.reason}" and cleanly: "${event.wasClean}"`
+    );
+    broadcast.postMessage("webSocketClosed");
+    webSocket = null;
+    clearInterval(intervalId);
+  };
+}
+
+function disconnect() {
+  if (webSocket == null) {
+    return;
+  }
+  webSocket.close();
+}
+
+self.addEventListener("install", (event) => {
+  self.skipWaiting().then(() => {
+    console.log("Service worker installed");
+  });
+});
+
+self.addEventListener("activate", (event) => {
+  event.waitUntil(
+    self.clients.claim().then(() => {
+      console.log("Service worker activated");
+    })
+  );
+});
+
+self.addEventListener("message", (event) => {
+  console.log(`web socket worker received message: ${event.data}`);
+  if (event.data.action === "connect") {
+    connect(event.data.url, event.data.ticket);
+  } else if (event.data.action === "disconnect") {
+    disconnect();
+  }
+});