Introduce primary taxon for product

Created a new association between Product and Primary Taxon using the existing Taxon model.

core/app/models/spree/product.rb

@@ -32,6 +32,7 @@ class Product < Spree::Base
 
     belongs_to :tax_category, class_name: 'Spree::TaxCategory', optional: true
     belongs_to :shipping_category, class_name: 'Spree::ShippingCategory', inverse_of: :products, optional: true
+    belongs_to :primary_taxon, class_name: 'Spree::Taxon', optional: true
 
     has_one :master,
       -> { where(is_master: true).with_discarded },

core/config/locales/en.yml

@@ -179,6 +179,8 @@ en:
         name: Name
         on_hand: On Hand
         price: Master Price
+        primary_taxon: Primary Taxon
+        primary_taxon_id: Primary Taxon
         promotionable: Promotable
         shipping_category: Shipping Category
         sku: Master SKU

core/db/migrate/20250207104016_add_primary_taxon_to_products.rb

@@ -0,0 +1,7 @@
+class AddPrimaryTaxonToProducts < ActiveRecord::Migration[7.0]
+  def change
+    change_table :spree_products do |t|
+      t.references :primary_taxon, { to_table: :spree_taxons }
+    end
+  end
+end

core/lib/spree/permitted_attributes.rb

@@ -78,7 +78,7 @@ module PermittedAttributes
       :meta_keywords, :price, :sku, :deleted_at,
       :option_values_hash, :weight, :height, :width, :depth,
       :shipping_category_id, :tax_category_id,
-      :taxon_ids, :option_type_ids, :cost_currency, :cost_price
+      :taxon_ids, :option_type_ids, :cost_currency, :cost_price, :primary_taxon_id
     ]
 
     @@property_attributes = [:name, :presentation]

core/spec/models/spree/product_spec.rb

@@ -452,6 +452,22 @@ class Extension < Spree::Base
           end
         end
       end
+
+      describe "primary_taxon" do
+        it 'should belong to primary_taxon' do
+          expect(Spree::Product.reflect_on_association(:primary_taxon).macro).to eq(:belongs_to)
+        end
+
+        it 'should be optional' do
+          association = Spree::Product.reflect_on_association(:primary_taxon)
+          expect(association.options[:optional]).to be(true)
+        end
+
+        it 'should have a class_name of Spree::Taxon' do
+          association = Spree::Product.reflect_on_association(:primary_taxon)
+          expect(association.class_name).to eq('Spree::Taxon')
+        end
+      end
     end
   end
 
@@ -709,4 +725,13 @@ class Extension < Spree::Base
       end
     end
   end
+
+  it 'is valid with or without a primary_taxon' do
+    product_with_taxon = create(:product, primary_taxon: create(:taxon))
+
+    product_without_taxon = create(:product, primary_taxon: nil)
+
+    expect(product_with_taxon).to be_valid
+    expect(product_without_taxon).to be_valid
+  end
 end