Fix AddPaymentSourcesToWallet changing default when reused

PR solidusio#2913 [1] changed how the new default WalletPaymentSource was set.
Before:
- using the last one found/created by the Order's PaymentSources

After:
- using the user's last WalletPaymentSource.

This is problematic in the scenario where the user uses their default
WalletPaymentSource for an order, but their default source is not their
most recent WalletPaymentSource.

Fixes issue solidusio#4004 [2]

Now, #make_default uses WalletPaymentSources found or created by the
order, it means it will keep the default payment source if used. This
is because wallet#add finds or creates.

[1] solidusio#2913
[2] solidusio#4004

core/app/models/spree/wallet/add_payment_sources_to_wallet.rb

@@ -24,19 +24,19 @@ def add_to_wallet
       # add valid sources to wallet and optionally set a default
       if sources.any?
         # arbitrarily sort by id for picking a default
-        sources.sort_by(&:id).each do |source|
+        order_wallet_payment_sources = sources.sort_by(&:id).map do |source|
           order.user.wallet.add(source)
         end
 
-        make_default
+        make_default(order_wallet_payment_sources)
       end
     end
   end
 
   protected
 
-  def make_default
-    order.user.wallet.default_wallet_payment_source = order.user.wallet_payment_sources.last
+  def make_default(sources)
+    order.user.wallet.default_wallet_payment_source = sources.last
   end
 
   private

core/spec/models/spree/wallet/add_payment_sources_to_wallet_spec.rb

@@ -4,6 +4,7 @@
 
 RSpec.describe Spree::Wallet::AddPaymentSourcesToWallet, type: :model do
   let(:order) { create(:order_ready_to_complete) }
+  let(:user) { order.user }
 
   describe '#add_to_wallet' do
     subject { described_class.new(order) }
@@ -13,5 +14,28 @@
         order.user.wallet.wallet_payment_sources.count
       }.by(1)
     end
+
+    context "when the default wallet payment source is used and more a recent wallet payment exists" do
+      before do
+        credit_card_one = user.wallet.add(create(:credit_card, user: user))
+        user.wallet.add(create(:credit_card, user: user))
+        user.wallet.default_wallet_payment_source = credit_card_one # must be the first created card
+        order.payments.first.update!(source: credit_card_one.payment_source)
+      end
+
+      it 'does not make a new wallet payment source' do
+        expect(user.wallet).to receive(:add).and_call_original
+        expect { subject.add_to_wallet }.to_not change {
+          order.user.wallet.wallet_payment_sources.count
+        }
+      end
+
+      it 'does change the default wallet payment source' do
+        expect(user.wallet).to receive(:add).and_call_original
+        expect { subject.add_to_wallet }.to_not change {
+          user.wallet.default_wallet_payment_source
+        }
+      end
+    end
   end
 end