Move building of Offer to the right module

The DfcBuilder was doing everything to start with but we are moving its
parts to smaller modules now.

engines/dfc_provider/app/controllers/dfc_provider/offers_controller.rb

@@ -5,7 +5,7 @@ module DfcProvider
     before_action :check_enterprise
 
     def show
-      subject = DfcBuilder.offer(variant)
+      subject = OfferBuilder.build(variant)
       render json: DfcIo.export(subject)
     end
 

engines/dfc_provider/app/services/dfc_builder.rb

@@ -12,22 +12,7 @@ class DfcBuilder
       id, product:,
           sku: variant.sku,
           stockLimitation: stock_limitation(variant),
-          offers: [offer(variant)],
-    )
-  end
-
-  def self.offer(variant)
-    # We don't have an endpoint for offers yet and this URL is only a
-    # placeholder for now. The offer is actually affected by order cycle and
-    # customer tags. We'll solve that at a later stage.
-    enterprise_url = urls.enterprise_url(id: variant.product.supplier_id)
-    id = "#{enterprise_url}/offers/#{variant.id}"
-    offered_to = []
-
-    DataFoodConsortium::Connector::Offer.new(
-      id, offeredTo: offered_to,
-          price: variant.price.to_f,
-          stockLimitation: stock_limitation(variant),
+          offers: [OfferBuilder.build(variant)],
     )
   end
 

engines/dfc_provider/app/services/offer_builder.rb

@@ -1,6 +1,19 @@
 # frozen_string_literal: true
 
 class OfferBuilder < DfcBuilder
+  def self.build(variant)
+    id = urls.enterprise_offer_url(
+      enterprise_id: variant.product.supplier_id,
+      id: variant.id,
+    )
+
+    DataFoodConsortium::Connector::Offer.new(
+      id,
+      price: variant.price.to_f,
+      stockLimitation: stock_limitation(variant),
+    )
+  end
+
   def self.apply(offer, variant)
     variant.on_hand = offer.stockLimitation
     variant.price = offer.price

engines/dfc_provider/spec/services/offer_builder_spec.rb

@@ -2,7 +2,7 @@
 
 require_relative "../spec_helper"
 
-describe DfcBuilder do
+describe OfferBuilder do
   let(:variant) { build(:variant) }
 
   describe ".offer" do
@@ -11,7 +11,7 @@ describe DfcBuilder do
       variant.save!
       variant.on_hand = 5
 
-      offer = DfcBuilder.offer(variant)
+      offer = OfferBuilder.build(variant)
 
       expect(offer.stockLimitation).to eq 5
     end
@@ -22,7 +22,7 @@ describe DfcBuilder do
       variant.on_hand = 5
       variant.on_demand = true
 
-      offer = DfcBuilder.offer(variant)
+      offer = OfferBuilder.build(variant)
 
       expect(offer.stockLimitation).to eq nil
     end