Now I have developed an app in Flutter and also added firebase_auth now what I want is that each user when is logged in could set a value to a variable, let's say variable your Phone Number which every user has to set once they log in not I want to ask if the user logs in another device how am I gonna make sure the variable Phone Number is same as he set in the other device.
I know that I could store that data locally using SQL or sharedpreferences but in firebase how should I do?