Tracking and engaging users are key features necessary for your app to grow. That means you should be able to register and authenticate users. Once the users start using the app, you also need to segment the users so that you can customize their interactions. Then, you can send push notifications to encourage users to revisit the app.

There are two components that you need to use for your project, as follows:

• Auth0: Auth0 is a cloud-based authentication service. The whole idea is that you delegate authentication of your application to Auth0. Auth0 supports many frameworks, including Ionic2+, and also supports many social providers for authentication such as Google and Facebook. On the top of that, they have excellent documentation.
• OneSignal: OneSignal is a service that allows us to send the push notification to both iOS and Android. As a matter of fact, it supports other platforms such as Windows, Web Push Notifications, Amazon Fire, and so on. The best part is, in general, we need different code for adding push notifications. But because of Cordova and OneSignal's abstract API, we only need to write push notification code once for both platforms.