Developer may integrate Compensated with their existing Rails App without wrapping it in custom model classes

[zspencer]

Now that we've gotten 3~4 implementations within Rails apps; it seems like a reasonable next step will be to create a Rails Engine that encourages a domain model.

Suggested Steps:

• Sprout a compensated-rails gem that is a sibling to compensated-ruby;
• Ensure that compensated-rails test suite gets executed across Ruby versions within CI
• Ensure that the compensated-rails test suite gets executed across Rails versions within CI
• Create a Compensated::Rails::Event resource and supporting migrations
• Create Compensated::Rails::Customer and Compensated::Rails::PaymentProfile resources so that we can associate events with the payments provider and the customer the events relate to.
• Update the compensated-rails-5-example to use the engine

I'm comfortable merging this into 0.X in small steps or one big PR; so long as it's not making significant changes to the compensated-ruby directory.

[user512]

This is our understanding between compensated-ruby & compensated-rails.

1. compensated-rails will depend on compensated-ruby.
2. compensated-ruby will be responsible for core logic, including parsing webhook event.
3. compensated-rails will be generating required tables and provide reader methods.
4. Existing users of compensated-ruby will be able to keep using that gem can expect further future code improvement without needed to transition to compensated-rails.

@zspencer Does these align with what you were thinking?

[zspencer]

Yep! this matches what I was imagining perfectly!