(core) Add telemetry

Test Plan: Server tests.

Reviewers: jarek

Differential Revision: https://phab.getgrist.com/D3818

app/client/lib/telemetry.ts

@@ -0,0 +1,23 @@
+import {logError} from 'app/client/models/errors';
+import {TelemetryEventName} from 'app/common/Telemetry';
+import {fetchFromHome, pageHasHome} from 'app/common/urlUtils';
+
+export async function logTelemetryEvent(name: TelemetryEventName, metadata?: Record<string, any>) {
+  if (!pageHasHome()) { return; }
+
+  await fetchFromHome('/api/telemetry', {
+    method: 'POST',
+    body: JSON.stringify({
+      name,
+      metadata,
+    }),
+    credentials: 'include',
+    headers: {
+      'Content-Type': 'application/json',
+      'X-Requested-With': 'XMLHttpRequest',
+    },
+  }).catch((e: Error) => {
+    console.warn(`Failed to log telemetry event ${name}`, e);
+    logError(e);
+  });
+}