Add support for setting cancellation_details (stripe-ruby-mock#937)

## What

Makes it possible to set cancellation_details when marking a
subscription for cancellation
https://docs.stripe.com/api/subscriptions/update#update_subscription-cancellation_details

Author: balvig

lib/stripe_mock/data.rb

@@ -420,6 +420,11 @@ def self.mock_subscription(params={})
         cancel_at_period_end: false,
         canceled_at: nil,
         collection_method: 'charge_automatically',
+        cancellation_details: {
+          comment: nil,
+          feedback: nil,
+          reason: nil
+        },
         ended_at: nil,
         start_date: 1308595038,
         object: 'subscription',

lib/stripe_mock/request_handlers/helpers/subscription_helpers.rb

@@ -46,6 +46,17 @@ def custom_subscription_params(plans, cus, options = {})
           params.merge!(cancel_at_period_end: false, canceled_at: nil)
         end
 
+        options.fetch(:cancellation_details, {}).each do |key, value|
+          next if value.nil?
+
+          if params[:cancel_at_period_end]
+            params[:cancellation_details] ||= {}
+            params[:cancellation_details][key] = value
+          else
+            raise Stripe::InvalidRequestError.new("`cancellation_details` can only be set on subscriptions that are set to cancel.", "cancellation_details", http_status: 400)
+          end
+        end
+
         # TODO: Implement coupon logic
 
         if (((plan && plan[:trial_period_days]) || 0) == 0 && options[:trial_end].nil?) || options[:trial_end] == "now"

spec/shared_stripe_examples/subscription_examples.rb

@@ -1220,6 +1220,41 @@
       expect(customer.subscriptions.count).to eq(0)
       expect(customer.subscriptions.data.length).to eq(0)
     end
+
+    it "supports adding a comment to cancellation_details" do
+      customer = Stripe::Customer.create(source: gen_card_tk, plan: plan.id)
+      subscription = Stripe::Subscription.retrieve(customer.subscriptions.data.first.id)
+
+      result = Stripe::Subscription.update(
+        subscription.id,
+        cancel_at_period_end: true,
+        cancellation_details: { comment: 'Cancelled by user' }
+      )
+
+      expect(result.cancellation_details.comment).to eq('Cancelled by user')
+    end
+
+    it "supports adding feedback to cancellation_details" do
+      customer = Stripe::Customer.create(source: gen_card_tk, plan: plan.id)
+      subscription = Stripe::Subscription.retrieve(customer.subscriptions.data.first.id)
+
+      result = Stripe::Subscription.update(
+        subscription.id,
+        cancel_at_period_end: true,
+        cancellation_details: { feedback: 'customer_service' }
+      )
+
+      expect(result.cancellation_details.feedback).to eq('customer_service')
+    end
+
+    it "raises an error if adding a comment to cancellation_details when not cancelling" do
+      customer = Stripe::Customer.create(source: gen_card_tk, plan: plan.id)
+      subscription = Stripe::Subscription.retrieve(customer.subscriptions.data.first.id)
+
+      expect do
+        Stripe::Subscription.update(subscription.id, cancellation_details: { comment: 'Cancelled by user' })
+      end.to raise_error Stripe::InvalidRequestError, /can only be set on subscriptions that are set to cancel./
+    end
   end
 
   it "supports 'cancelling' by updating cancel_at_period_end" do
@@ -1328,6 +1363,10 @@
     it "has a start_date attribute" do
       expect(subscription).to respond_to(:start_date)
     end
+
+    it "has cancellation_details" do
+      expect(subscription).to respond_to(:cancellation_details)
+    end
   end
 
   context "retrieve multiple subscriptions" do