Fix user session storing without scopes

[paulomarg]

What this PR does

We had updated the UserSessionStorageWithScopes class to fix an issue where the type of the user param was incorrect, but the same issue was present in UserSessionStorage. This PR fixes that to properly call user.id to access the AssociatedUser property.

Reviewer's guide to testing

You'll need to create an app with a few conditions:

• It has User sessions (rails g shopify_app:user_model)
  • Answer n when prompted if you want to add user scopes
• Make sure the User model is using the include ShopifyApp::UserSessionStorage concern (not ShopifyApp::UserSessionStorageWithScopes
• Set config.reauth_on_access_scope_changes = false in the shopify_app initializer
• Set config.user_session_repository = "User"

Things to focus on

Before this branch, that would lead into an infinite auth loop. With this fix, the app should authenticate normally, and there should be an entry in both the users and shops tables.

Checklist

Before submitting the PR, please consider if any of the following are needed:

• Update CHANGELOG.md if the changes would impact users

[lilypustovyk]

😍
Thank you for addressing this!

[nelsonwittwer]

🎉 for finding this hidden bug!