Refactor: move variant duplication to model

I tried to avoid it but rubocop made me move it. I think maybe it will need to go into a concern or service class later, but hopefully it's ok here for now.

app/controllers/admin/products_v3_controller.rb

@@ -116,15 +116,7 @@ module Admin
       status = :ok
 
       begin
-        variant = source_variant.dup #may need a VariantDuplicator like producs?
-        variant.price = source_variant.price
-        variant.save!
-        variant.source_variants << source_variant
-        # Owner is my enterprise which has permission to create sourced variants from that supplier
-        variant.owner_id = EnterpriseRelationship.permitted_by(source_variant.supplier).permitting(spree_current_user.enterprises).with_permission(:create_sourced_variants).pluck(:child_id).first
-        variant.on_demand = source_variant.on_demand
-        variant.on_hand = source_variant.on_hand
-        variant.save!
+        variant = source_variant.create_sourced_variant(spree_current_user)
 
         flash.now[:success] = t('.success')
         variant_index = "-#{variant.id}"

app/models/spree/variant.rb

@@ -273,6 +273,24 @@ module Spree
       @on_hand_desired = ActiveModel::Type::Integer.new.cast(val)
     end
 
+    # Clone this variant, retaining a 'source' link to it
+    def create_sourced_variant(user)
+      # Owner is my enterprise which has permission to create sourced variants from that supplier
+      owner_id = EnterpriseRelationship.permitted_by(supplier).permitting(user.enterprises)
+        .with_permission(:create_sourced_variants)
+        .pick(:child_id)
+
+      dup.tap do |variant|
+        variant.price = price
+        variant.save!
+        variant.source_variants = [self]
+        variant.owner_id = owner_id
+        variant.on_demand = on_demand
+        variant.on_hand = on_hand
+        variant.save!
+      end
+    end
+
     private
 
     def check_currency

spec/models/spree/variant_spec.rb

@@ -1005,4 +1005,34 @@ RSpec.describe Spree::Variant do
       expect(variant.unit_presentation).to eq "My display"
     end
   end
+
+  describe "#create_sourced_variant" do
+    let(:user) { create(:user, enterprises: [enterprise]) }
+    let(:supplier) { variant.supplier }
+    let(:enterprise) { create(:enterprise) }
+
+    context "with create_sourced_variants permissions on supplier" do
+      let!(:enterprise_relationship) {
+        create(:enterprise_relationship,
+               parent: supplier,
+               child: enterprise,
+               permissions_list: [:create_sourced_variants])
+      }
+
+      it "clones the variant, retaining a link to the source" do
+        variant.price = 10.95
+        variant.save!
+        variant.on_demand = false
+        variant.on_hand = 5
+
+        sourced_variant = variant.create_sourced_variant(user)
+
+        expect(sourced_variant.source_variants).to eq [variant]
+        expect(sourced_variant.owner).to eq enterprise
+        expect(sourced_variant.price).to eq 10.95
+        expect(sourced_variant.on_demand).to eq false
+        expect(sourced_variant.on_hand).to eq 5
+      end
+    end
+  end
 end