[#68239646] One Shipping Address Per Subscription

* Add ship_address to line item
[#68239646] One Shipping Address Per Subscription

* Adds stock splitter
[#68239646] One Shipping Address Per Subscription

* Adds module custom model naming
* Extend spree product with module custom model naming
Adds factories for easy load
[#68239646] One Shipping Address Per Subscription

* Adds methods to define if it is a subscription product
[#68239646] One Shipping Address Per Subscription

* Overrides add_to_line_item to let only one subscription per line item
[#68239646] One Shipping Address Per Subscription

* Deletes unneded migration
* Adds migration for adding line item id to spree addresses
[#68239646] One Shipping Address Per Subscription

* Adss address spliter as first splitter for spree
[#68239646] One Shipping Per Subscription

* Updates address splitter to extract shipping address id from address
[#68239646] One Shipping Per Subscription

* Refactors orders decorator
[#68239646] One Shipping Per Subscription

* Adds nested forms for line item shipping addresses
[#68239646] One Shipping Address Per Subscription

* Adds line items attributes to checkout permitted attributes
[#68239646] One Shipping Per Subscription

* Overrides spree address form address_id assignment
* Send address_id to form rendering for subscription addresses
Remove duplicated factories
[#68239646] One Shipping Per Subscription

* Adds sotck splitter address spec
* Refactor comments from @efigarolam
[68239646] One shipping address per subscription

* Added test for subscription_product
* Added test for product
Merge pull request #7 from stevenbarragan/feature/shipping-per-subscription

Allows to have one shipping address per subscription