What are some options for logging into a react application from a different react application on another domain?

Question

I'm trying to create a user auth application that stores all of our user data and is then used to login to our various applications that we have created. We plan on really using this application as our user governance. But for now our other applications have their own logins.

Currently we have a button for each application, when the button is clicked a new window for that application should open and the user should be logged in.

The way I have started is by creating an api request to login route on the backend of the application being clicked. It works, but I don't know what to do with the information received. Our other application looks to local storage to see if there is a 'user' , so the problem is getting the information received in the auth app to the local storage of the other app. I have tried using this cross-domain-storage package which utilizes the Window: message event but I'm getting a bunch of errors, I don't think it's the correct way to go. I've considered implementing the Window: message event on my own, but again, I don't know if that's the correct way to go on this.

I don't know if using the endpoint like I am doing is the correct way of doing this, if there are any other suggestions please let me know.