I am trying to implement a two step authentication system in my app.
I have already completed the part where the user is registering with Firebase and the other technicalities. The user is required to provide a phone number when registering. Now, the users will log-in with their e-mail address and password.
What I am trying to implement is a system where Firebase sends a verification code to the users' phone after they have logged in. Then the user is required to introduce the code to be able to complete the log in process.
Could you provide me with some sources or advice regarding this situation? Just some guidelines regarding on how I should approach this scenario.