Here is a possible revision:
I'm not sure if I'm describing the scenario accurately, but here's a rough overview. An app has its own user system, with mobile numbers or email addresses as the main login methods. The app wants to integrate a Flarum forum (or another open-source forum) as a user communication community. When users click on the forum tab, they should be automatically logged in with their app username as the account, even though this involves cross-domain activity (different domains, like flarum.example.com). The app does not want users to have to register or log in again.
Is it possible to use the following method? The app sends encrypted user account information (mobile number/email or unique ID), login status (cookie? token?), and user identity information from the app (regular registered user, product category as tag label for N products, VIP status information for non-VIP users who pay per use versus VIP users who pay monthly or yearly) to the forum. The forum would decrypt and register the user directly, assigning the user's identity according to the app's logic. All this should take less than 1 second to complete, and ideally the user should not even be aware of these actions.
Is this technically feasible? Are there any interested individuals who would like to try and help with this project for a fee? Thank you.