Changes to Create a paypal gateway

added the new optional request property data/attributes/idempotency_window_mins

added the optional property data/attributes/idempotency_window_mins to the response with the 201 status

request property data/type was restricted to a list of enum values

added the new optional request property data/attributes/_check

added the new optional request property data/attributes/_disable

added the new optional request property data/attributes/_enable

added the new optional request property data/attributes/force_payments

the type request property default value paypal_gateways was removed

added the new paypal_gateways enum value to the request property data/type

added the media type application/vnd.api+json for the response with the status 201