I am developing a mobile IOS appp which will consume some data from Firebase. I need to implement functionality so that only authenticated users, who have paid a monthly subscription will be able to continue using my App. I would like to know if this kind of functionality can be built for an IOS App using Firebase's email based authentication. If email based authentication cannot help me implement this functionality, please let me know if Firebase's custom authentication would help me achieve this. I would also appreciate advice if there are any other reliable alternative backend services available that can help me implement this kind of functionality for my App without me needing to do too much work as I do not have technical expertise to develop this part of the functionality for my App.
Thank you for your help.