Replace oauth_user_info with custom getter method

[moshthepitt]

In flask appbuilder it seems that they suggest the correct way to provide a custom user info getter method is as below:

@appbuilder.sm.oauth_user_info_getter
def my_oauth_user_info(sm, provider, response=None):
    if provider == 'github':
        me = sm.oauth_remotes[provider].get('user')
        return {'username': me.data.get('login')}
    else:
        return {}

We need to investigate if indeed this is the recommended approach and then implement it if so.