fix: login from storefront

[kieckhafer]

See reactioncommerce/reaction#5951

Impact: critical
Type: bugfix

You need to be this branch of Reaction when testing. That PR and this one should be merged at the same time.

Issue

Account login was not working when trying to login via example storefront.

Solution

Add oauth login method to new AuthContainer. This is how we used to do oauth login in the past, when we used OauthContainer, but this was removed / with the new AuthContainer.

Breaking changes

None

Testing

1. Start the full app (reaction (fix: login from storefront reaction#5951) / storefront)
2. Navigate to storefront
3. Login
4. See you are redirected back to storefront, and you are logged in
5. Logout
6. See you are redirected back to storefront, and are logged out

[manueldelreal]