Remove deprecated offset_payments

This was a leftover for a feature that has been removed long time ago.
Please use Refunds now.

Ref solidusio#5008

core/app/models/spree/order.rb

@@ -559,8 +559,7 @@ def quantity
     end
 
     def has_non_reimbursement_related_refunds?
-      refunds.non_reimbursement.exists? ||
-        payments.where("source_type = 'Spree::Payment' AND amount < 0 AND state = 'completed'").exists? # how old versions of spree stored refunds
+      refunds.non_reimbursement.exists?
     end
 
     def tax_total

core/app/models/spree/payment.rb

@@ -16,7 +16,6 @@ class Payment < Spree::Base
     belongs_to :source, polymorphic: true, optional: true
     belongs_to :payment_method, -> { with_discarded }, class_name: 'Spree::PaymentMethod', inverse_of: :payments, optional: true
 
-    has_many :offsets, -> { offset_payment }, class_name: "Spree::Payment", foreign_key: :source_id
     has_many :log_entries, as: :source
     has_many :state_changes, as: :stateful
     has_many :capture_events, class_name: 'Spree::PaymentCaptureEvent'
@@ -45,19 +44,6 @@ class Payment < Spree::Base
 
     scope :from_credit_card, -> { where(source_type: 'Spree::CreditCard') }
     scope :with_state, ->(state) { where(state: state.to_s) }
-    # "offset" is reserved by activerecord
-    # TODO: When removing the method we can also:
-    #   - Remove the `.offsets` association
-    #   - Remove the `#offsets_total` method
-    #   - Remove offsets count from the `#credit_allowed` method
-    #   - Remove offsets check from `Spree::Order#has_non_reimbursement_related_refunds?
-    def self.offset_payment
-      Spree::Deprecation.warn <<~MSG
-        `Spree::Payment offsets` are deprecated. Use the refund system (`Spree::Refund`) instead.
-      MSG
-
-      where("source_type = 'Spree::Payment' AND amount < 0 AND state = 'completed'")
-    end
 
     scope :checkout, -> { with_state('checkout') }
     scope :completed, -> { with_state('completed') }
@@ -100,22 +86,11 @@ def amount=(amount)
         end || amount
     end
 
-    # The total amount of the offsets (for old-style refunds) for this payment.
-    #
-    # @return [BigDecimal] the total amount of this payment's offsets
-    def offsets_total
-      offsets.pluck(:amount).sum
-    end
-
     # The total amount this payment can be credited.
     #
-    # @return [BigDecimal] the amount of this payment minus the offsets
-    #   (old-style refunds) and refunds
+    # @return [BigDecimal] the amount of this payment minus refunds
     def credit_allowed
-      amount - (
-        (self.class.where("source_type = 'Spree::Payment' AND amount < 0 AND state = 'completed' AND source_id = ?", id).sum(:amount)).abs +
-        refunds.sum(:amount)
-      )
+      amount - refunds.sum(:amount)
     end
 
     # @return [Boolean] true when this payment can be credited

core/spec/models/spree/order_spec.rb

@@ -1122,19 +1122,6 @@ def generate
       it { is_expected.to eq true }
     end
 
-    context 'an old-style refund exists' do
-      let(:order) { create(:order_ready_to_ship) }
-      let(:payment) { order.payments.first.tap { |p| allow(p).to receive_messages(profiles_supported?: false) } }
-      let!(:refund_payment) {
-        build(:payment, amount: -1, order: order, state: 'completed', source: payment).tap do |p|
-          allow(p).to receive_messages(profiles_supported?: false)
-          p.save!
-        end
-      }
-
-      it { is_expected.to eq true }
-    end
-
     context 'a reimbursement related refund exists' do
       let(:order) { refund.payment.order }
       let(:refund) { create(:refund, reimbursement_id: 123, amount: 5, payment_amount: 14) }

core/spec/models/spree/payment_spec.rb

@@ -668,14 +668,6 @@
   end
 
   describe "#credit_allowed" do
-    # Regression test for https://github.com/spree/spree/issues/4403 and https://github.com/spree/spree/issues/4407
-    it "is the difference between offsets total and payment amount" do
-      payment.amount = 100
-      expect(payment.credit_allowed).to eq(100)
-      create(:payment, amount: -80, source: payment, source_type: 'Spree::Payment', state: 'completed', payment_method: create(:check_payment_method))
-      expect(payment.credit_allowed).to eq(20)
-    end
-
     it "is the difference between refunds total and payment amount" do
       payment.amount = 100
 
@@ -1339,18 +1331,4 @@
       expect(described_class.valid).to be_empty
     end
   end
-
-  describe '::offset_payment' do
-    it 'is deprecated' do
-      expect(Spree::Deprecation).to receive(:warn).with(/offsets` are deprecated/)
-
-      described_class.offset_payment
-    end
-
-    it 'still calls the original method' do
-      Spree::Deprecation.silence do
-        expect(described_class.offset_payment.class.name).to eq('ActiveRecord::Relation')
-      end
-    end
-  end
 end