How do we link oauth identity with local identity?

I am trying to build a mobile application in React Native that allows "social" login, i.e. Google, Facebook, Instagram, GitHub, etc. I had a few questions regarding this:

1. How do I handle user account creation on the backend, i.e. once a user authenticates with (say) Google on the app using, for example, the react-native-google-signin plugin, how do I create an account for that user on my backend?

2. If my backend has to use the client credentials to obtain the data for registration (e.g. user email, first name, last name) from the service, would I have to implement a separate connection for each service against which I want to authenticate?

3. If my backend is written in Django, are there Django plugins that allow me to do this out-of-the-box?