feat: Add support for the session init event. (#738)

This PR adds an event which is emitted when a session is started.

It also removes some unused code related to session replay.

BEGIN_COMMIT_OVERRIDE
feat: Add support for the session init event.
chore: Remove session capture until session replay is added.
END_COMMIT_OVERRIDE

packages/telemetry/browser-telemetry/__tests__/BrowserTelemetryImpl.test.ts

@@ -67,8 +67,8 @@ it('limits pending events to maxPendingEvents', () => {
 
   telemetry.register(mockClient);
 
-  // Should only see the last 2 errors tracked
-  expect(mockClient.track).toHaveBeenCalledTimes(2);
+  // Should only see the the session init event and last 2 errors tracked
+  expect(mockClient.track).toHaveBeenCalledTimes(3);
   expect(mockClient.track).toHaveBeenCalledWith(
     '$ld:telemetry:error',
     expect.objectContaining({
@@ -522,3 +522,15 @@ it('uses the client logger when no logger is provided', () => {
     'LaunchDarkly - Browser Telemetry: Error applying breadcrumb filters: Error: Filter error',
   );
 });
+
+it('sends session init event when client is registered', () => {
+  const telemetry = new BrowserTelemetryImpl(defaultOptions);
+  telemetry.register(mockClient);
+
+  expect(mockClient.track).toHaveBeenCalledWith(
+    '$ld:telemetry:session:init',
+    expect.objectContaining({
+      sessionId: expect.any(String),
+    }),
+  );
+});

packages/telemetry/browser-telemetry/src/BrowserTelemetryImpl.ts

@@ -28,7 +28,7 @@ import { getTraceKit } from './vendor/TraceKit';
 
 const CUSTOM_KEY_PREFIX = '$ld:telemetry';
 const ERROR_KEY = `${CUSTOM_KEY_PREFIX}:error`;
-const SESSION_CAPTURE_KEY = `${CUSTOM_KEY_PREFIX}:sessionCapture`;
+const SESSION_INIT_KEY = `${CUSTOM_KEY_PREFIX}:session:init`;
 const GENERIC_EXCEPTION = 'generic';
 const NULL_EXCEPTION_MESSAGE = 'exception was null or undefined';
 const MISSING_MESSAGE = 'exception had no message';
@@ -163,6 +163,9 @@ export default class BrowserTelemetryImpl implements BrowserTelemetry {
     // When the client is registered, we need to set the logger again, because we may be able to use the client's
     // logger.
     this._setLogger();
+
+    this._client.track(SESSION_INIT_KEY, { sessionId: this._sessionId });
+
     this._pendingEvents.forEach((event) => {
       this._client?.track(event.type, event.data);
     });
@@ -237,10 +240,6 @@ export default class BrowserTelemetryImpl implements BrowserTelemetry {
     this.captureError(errorEvent.error);
   }
 
-  captureSession(sessionEvent: EventData): void {
-    this._capture(SESSION_CAPTURE_KEY, { ...sessionEvent, breadcrumbs: [...this._breadcrumbs] });
-  }
-
   private _applyBreadcrumbFilters(
     breadcrumb: Breadcrumb,
     filters: BreadcrumbFilter[],