How do I create a custom Django AllAuth Socialaccount model?

Question

Here is a summary of app I am attempting to create:

I want users (who are primarily students) to register in my app using their Google Accounts. The service I am using to manage this creation of accounts is Django-AllAuth. Django-AllAuth has a very limited Social Account Model (it only saves username, email, name and their roles).

I want to have further fields that I save in my DB. I want to save my users' Year Group and Favourite Subject.

How a user registers on my website:

User is redirected to a "Sign in With Google" page. Google will return the following fields: the user's name, Google ID and email.

Then, I want to prompt the user to a "Finish registering Account" page. In this page, the user will have to fill out input fields for their Username, Year Group and Favourite Subject

I cannot find any solutions for this specific case.

My Questions

How do I create a custom Social Accounts Model in Django-AllAuth?

How do I ask users to fill out another Finishing Registering Form?

I am aware that you can redirect users to a Finishing Registering Form via this code in the settings.py file. However, this form only consists of the "email" and "username" fields.

SOCIALACCOUNT_AUTO_SIGNUP=False

Here is my AllAuth Configuration (in settings.py):

SOCIALACCOUNT_AUTO_SIGNUP=False
SOCIALACCOUNT_LOGIN_ON_GET=False
SOCIALACCOUNT_EMAIL_REQUIRED=True
ACCOUNT_USERNAME_REQUIRED=True
ACCOUNT_UNIQUE_EMAIL=True

SOCIALACCOUNT_PROVIDERS = {
    'google': {
        'SCOPE': [
            'profile',
            'email',
        ],
        'AUTH_PARAMS': {
            'access_type': 'offline',
        }
    }
}