fix: Various fixes for collaborative editing beta (#2561)

* fix: Remove Saving… message when collab enabled

* chore: Add tracing extension to collaboration server

* fix: Incorrect debounce behavior due to missing timestamps on events, fixes abundence of notifications when editing in realtime collab mode

* fix: Reload document prompt when collab editing

server/collaboration/tracing.js

@@ -0,0 +1,40 @@
+// @flow
+import * as metrics from "../utils/metrics";
+
+let count = 0;
+
+export default class Tracing {
+  async onCreateDocument({ documentName }: { documentName: string }) {
+    metrics.increment("collaboration.create_document", { documentName });
+
+    // TODO: Waiting for `instance` available in payload
+    // metrics.gaugePerInstance(
+    //   "collaboration.documents_count",
+    //   instance.documents.size()
+    // );
+  }
+
+  async onAuthenticationFailed({ documentName }: { documentName: string }) {
+    metrics.increment("collaboration.authentication_failed", { documentName });
+  }
+
+  async onConnect({ documentName }: { documentName: string }) {
+    metrics.increment("collaboration.connect", { documentName });
+    metrics.gaugePerInstance("collaboration.connections_count", ++count);
+  }
+
+  async onDisconnect({ documentName }: { documentName: string }) {
+    metrics.increment("collaboration.disconnect", { documentName });
+    metrics.gaugePerInstance("collaboration.connections_count", --count);
+
+    // TODO: Waiting for `instance` available in payload
+    // metrics.gaugePerInstance(
+    //   "collaboration.documents_count",
+    //   instance.documents.size()
+    // );
+  }
+
+  async onChange({ documentName }: { documentName: string }) {
+    metrics.increment("collaboration.change", { documentName });
+  }
+}