Remove unused ShippingRateTaxer service object

core/app/models/spree/shipping_rate_tax.rb

@@ -5,7 +5,7 @@ module Spree
   # @attr [Spree::ShippingRate] shipping_rate The shipping rate to be taxed
   # @attr [Spree::TaxRate] tax_rate The tax rate used to calculate the tax amount
   # @since 1.3.0
-  # @see Spree::Tax::ShippingRateTaxer
+  # @see Spree::Stock::Estimator
   class ShippingRateTax < Spree::Base
     belongs_to :shipping_rate, class_name: "Spree::ShippingRate", optional: true
     belongs_to :tax_rate, class_name: "Spree::TaxRate", optional: true

core/app/models/spree/tax_calculator/shipping_rate.rb

@@ -9,7 +9,7 @@ module TaxCalculator
     # looking to provide their own calculator should adhere to the API of this
     # class.
     #
-    # @see Spree::Tax::ShippingRateTaxer
+    # @see Spree::Stock::Estimator
     class ShippingRate
       include Spree::Tax::TaxHelpers
 

core/spec/models/spree/shipping_rate_spec.rb

@@ -38,7 +38,10 @@
       let(:order_address) { address }
 
       before do
-        Spree::Tax::ShippingRateTaxer.new.tax(shipping_rate)
+        shipping_rate.taxes.build(
+          amount: 0.91,
+          tax_rate: tax_rate,
+        )
       end
 
       it "shows correct tax amount" do
@@ -68,7 +71,10 @@
       let(:order_address) { address }
 
       before do
-        Spree::Tax::ShippingRateTaxer.new.tax(shipping_rate)
+        shipping_rate.taxes.build(
+          amount: 1.0,
+          tax_rate: tax_rate,
+        )
       end
 
       it "shows correct tax amount" do
@@ -107,7 +113,15 @@
       let(:order_address) { address }
 
       before do
-        Spree::Tax::ShippingRateTaxer.new.tax(shipping_rate)
+        shipping_rate.taxes.build(
+          amount: 1.0,
+          tax_rate: tax_rate,
+        )
+
+        shipping_rate.taxes.build(
+          amount: 0.5,
+          tax_rate: other_tax_rate,
+        )
       end
 
       it "shows correct tax amount" do