Implementation of 0Auth calendar sync with MongoDB Realm

We’re implementing a google and outlook calendar syncing solution for Ionic React and MongoDB - we’ve got to the point where data is fetched from the google calendar API, however the Oauth link is not currently working for more than one user however, As of right now, the Oauth Authentication system is flawed. The current flow is as follows: The user makes a request to the HTTPS endpoint defined in the realm cloud console (/authorizer) The endpoint makes an OAuth request to the Google servers to obtain the access code (this displays the google sign-in page to the user for them to allow access to their Google account) The Google server redirects back to the same HTTPS endpoint with the access code to request an access and refresh token At this point, the initial realm user details passed through the first request are no longer existent, as we cannot control the data passed back through googles redirect URI Mongo stores the access token in the database with no associated user (we need to assign this to a user) What we require is: The user makes a request to the HTTPS endpoint (or a function) The endpoint makes a request to the server to obtain the access code, and a pop up is displayed to the user to enter their google details The access code is transmitted to the HTTPS endpoint with the Realm users details The endpoint requests tokens from google and stores them in the database along with the Realm users ID This comes with a few speed bumps: An app CANNOT use the ionic built in browser, as this exposes certain security risks and is not allowed by apple or google The same endpoint CANNOT be used for both the access code and the token request, as the realm user data is lost in the process. Either the access code must be obtained within the app itself, or the realm user data must persist between obtaining the access code and making the token request