Add auto-capture functionality to Stripe integration

With this commit, the Solidus auto-capture feature has been incorporated into
the Stripe integration through the use of the auto_capture flag in
the Spree::PaymentMethod base model.
Stripe `capture_method` is now auto configured during the intent creation with
 "manual" or "automatic" based on the auto_capture flag in the related
payment method.

More information can be found in the Stripe documentation:
https://stripe.com/docs/api/payment_intents/object#payment_intent_object-capture_method

app/models/solidus_stripe/payment_intent.rb

@@ -35,6 +35,9 @@ def process_payment
       when 'requires_capture'
         payment.pend! unless payment.pending?
         successful = true
+      when 'succeeded'
+        payment.complete! unless payment.completed?
+        successful = true
       else
         payment.failure!
         successful = false
@@ -81,7 +84,7 @@ def create_stripe_intent(**stripe_intent_options)
             order.currency,
           ),
           currency: order.currency,
-          capture_method: 'manual',
+          capture_method: payment_method.auto_capture? ? 'automatic' : 'manual',
           setup_future_usage: payment_method.preferred_setup_future_usage.presence,
           customer: stripe_customer_id,
           metadata: { solidus_order_number: order.number },

spec/support/solidus_stripe/checkout_test_helper.rb

@@ -23,8 +23,12 @@ def assigns_guest_token(guest_token)
     # rubocop:enable RSpec/AnyInstance
   end
 
-  def creates_payment_method(setup_future_usage: 'off_session')
-    @payment_method = create(:stripe_payment_method, preferred_setup_future_usage: setup_future_usage)
+  def creates_payment_method(setup_future_usage: 'off_session', auto_capture: false)
+    @payment_method = create(
+      :stripe_payment_method,
+      preferred_setup_future_usage: setup_future_usage,
+      auto_capture: auto_capture
+    )
   end
 
   def payment_method
@@ -222,6 +226,15 @@ def payment_intent_is_created_with_required_capture
     expect(intent.status).to eq('requires_capture')
   end
 
+  def payment_intent_is_created_and_successfully_captured
+    order = Spree::Order.last
+    intent = SolidusStripe::PaymentIntent.where(
+      payment_method: payment_method,
+      order: order
+    ).last.stripe_intent
+    expect(intent.status).to eq('succeeded')
+  end
+
   def payment_intent_is_created_with_required_action
     order = Spree::Order.last
     intent = SolidusStripe::PaymentIntent.where(
@@ -295,14 +308,19 @@ def declined_cards_at_intent_creation_are_notified
     end
   end
 
-  def successfully_creates_a_payment_intent(user: nil)
+  def successfully_creates_a_payment_intent(user: nil, auto_capture: false)
     visits_payment_step(user: user)
     chooses_new_stripe_payment
     fills_stripe_form
 
     submits_payment
 
     completes_order
-    payment_intent_is_created_with_required_capture
+
+    if auto_capture
+      payment_intent_is_created_and_successfully_captured
+    else
+      payment_intent_is_created_with_required_capture
+    end
   end
 end

spec/system/frontend/solidus_stripe/checkout_spec.rb

@@ -27,6 +27,14 @@
     end
   end
 
+  context 'when auto-capture is enabled' do
+    it 'creates a payment intent and automatically processes payment' do
+      creates_payment_method(auto_capture: true)
+
+      successfully_creates_a_payment_intent(user: create(:user), auto_capture: true)
+    end
+  end
+
   context 'with a registered user' do
     ['on_session', 'off_session'].each do |setup_future_usage|
       context "when setup_future_usage is set with '#{setup_future_usage}'" do