Point deprecations to migration guide

Author: djhoughton

lib/shopify_api/resources/product.rb

@@ -17,7 +17,9 @@ def price_range
     end
 
     def total_inventory=(new_value)
-      raise(ShopifyAPI::ValidationException, 'deprecated behaviour') unless Base.api_version < ApiVersion.find_version('2019-10')
+      raise(ShopifyAPI::ValidationException,
+        "'total_inventory' is deprecated - see https://help.shopify.com/en/api/guides/inventory-migration-guide",
+        ) unless Base.api_version < ApiVersion.find_version('2019-10')
       super
     end
 

lib/shopify_api/resources/variant.rb

@@ -6,17 +6,23 @@ class Variant < Base
     conditional_prefix :product
 
     def inventory_quantity_adjustment=(new_value)
-      raise(ShopifyAPI::ValidationException, 'deprecated behaviour') unless Base.api_version < ApiVersion.find_version('2019-10')
+      raise(ShopifyAPI::ValidationException,
+        "'inventory_quantity_adjustment' is deprecated - see https://help.shopify.com/en/api/guides/inventory-migration-guide",
+        ) unless Base.api_version < ApiVersion.find_version('2019-10')
       super
     end
 
     def inventory_quantity=(new_value)
-      raise(ShopifyAPI::ValidationException, 'deprecated behaviour') unless Base.api_version < ApiVersion.find_version('2019-10')
+      raise(ShopifyAPI::ValidationException,
+        "'inventory_quantity' is deprecated - see https://help.shopify.com/en/api/guides/inventory-migration-guide",
+        ) unless Base.api_version < ApiVersion.find_version('2019-10')
       super
     end
 
     def old_inventory_quantity=(new_value)
-      raise(ShopifyAPI::ValidationException, 'deprecated behaviour') unless Base.api_version < ApiVersion.find_version('2019-10')
+      raise(ShopifyAPI::ValidationException,
+        "'old_inventory_quantity' is deprecated - see https://help.shopify.com/en/api/guides/inventory-migration-guide",
+        ) unless Base.api_version < ApiVersion.find_version('2019-10')
       super
     end
   end