Create OmniAuthConfiguration object to build future OmniAuth strategies

[NabeelAhsen]

This PR introduces the following:

1. A new OmniAuthConfiguration object
2. New configurations for ShopifyApp.configuration

• shop_access_scopes: These default to the old ShopifyApp.configuration.scope config
• user_access_scopes: These default to the old ShopifyApp.configuration.scope config

The intent is to use this object in the future to help us define and build omniauth strategies. This will be especially important in upcoming changes related to scope changes.

Here's how partners can use this in their omniauth.rb files:

Rails.application.config.middleware.use(OmniAuth::Builder) do
  provider :foo
      api_key,
      secret,
      scope: 'read_products',
      setup: lambda { |env|
        configuration = ShopifyApp::OmniauthConfiguration.new(env['omniauth.strategy'], Rack::Request.new(env))
        configuration.build_options
      }
end

For now, this class is not being used anywhere else in the library. A future PR will introduce default strategies for partners who use offline access tokens saved in their Shop records and online access tokens saved in their User records.

Based on the parent branch: https://github.com/Shopify/shopify_app/compare/scope-strategies

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

• Update CHANGELOG.md if the changes would impact users
• Update README.md, if appropriate.
• Update any relevant pages in docs/, if necessary
• For security fixes, the Disclosure Policy must be followed.

[rezaansyed]

🍞

[andyw8]

It seems a little odd to return a singular item scope when the method name implies a collection.

[rezaansyed]

Agreed! However, the scope attribute has been used to define a collection of scopes stored in a string for a while now. Changing this will be a breaking change for shopify_app developers.

[NabeelAhsen]

Good point, we can mark this as future work to update scope to scopes.

[jmndoza]

is this implementation still valid? I can't find any reference to OmniAuthConfiguration, I would like to modify ShopifyApp.configuration (and ShopifyAPI::Context.setup) in runtime