I am still studying programming for apps, I am with a doubt that for you should be simple, I created an app and an application Rest the user makes the registration in the app and saved the data in a MySQL database, when the user logs I save his data locally using sqlite for when he close the app and open again I check if it is already logged in or not, so long ... now I'm implementing a login button with Facebook, and I'm lost, I even managed to do the whole implementation and it's working, my question is:
When logging in via Facebook should I save this data also in MySQL, or do I let Facebook manage it? In the registered users they can change their data in the app like email and password and when it is via Facebook how is it?