Fix Security flaws on google oauth and create test for oauth modules

Deskripsi

Fix issue 15 dan membuat test untuk module oauth.

Beberapa concern:

AUTHENTICATION_BACKENDS = [
    # Default backend -- used to login by username in Django admin
    # This allow inactive user to authenticate
    'django.contrib.auth.backends.AllowAllUsersModelBackend',
    # `allauth` specific authentication methods, such as login by e-mail
    "allauth.account.auth_backends.AuthenticationBackend",
]

Saya harus membiarkan akun inactive dapat diautentikasi oleh modul django.contrib.auth dengan fungsi authenticate.