Promotions: Remove optional from belongs_to declarations

All of these have foreign key constraints set and are actually necessary
for the respective records to function.

Author: mamhoff

promotions/app/models/solidus_promotions/condition.rb

@@ -6,7 +6,7 @@ module SolidusPromotions
   class Condition < Spree::Base
     include Spree::Preferences::Persistable
 
-    belongs_to :benefit, class_name: "SolidusPromotions::Benefit", inverse_of: :conditions, optional: true
+    belongs_to :benefit, class_name: "SolidusPromotions::Benefit", inverse_of: :conditions
     has_one :promotion, through: :benefit
 
     scope :of_type, ->(type) { where(type: type) }

promotions/app/models/solidus_promotions/condition_product.rb

@@ -2,7 +2,7 @@
 
 module SolidusPromotions
   class ConditionProduct < Spree::Base
-    belongs_to :condition, class_name: "SolidusPromotions::Condition", optional: true
-    belongs_to :product, class_name: "Spree::Product", optional: true
+    belongs_to :condition, class_name: "SolidusPromotions::Condition"
+    belongs_to :product, class_name: "Spree::Product"
   end
 end

promotions/app/models/solidus_promotions/condition_store.rb

@@ -2,7 +2,7 @@
 
 module SolidusPromotions
   class ConditionStore < Spree::Base
-    belongs_to :condition, class_name: "SolidusPromotions::Condition", optional: true
-    belongs_to :store, class_name: "Spree::Store", optional: true
+    belongs_to :condition, class_name: "SolidusPromotions::Condition"
+    belongs_to :store, class_name: "Spree::Store"
   end
 end

promotions/app/models/solidus_promotions/condition_taxon.rb

@@ -2,7 +2,7 @@
 
 module SolidusPromotions
   class ConditionTaxon < Spree::Base
-    belongs_to :condition, class_name: "SolidusPromotions::Condition", optional: true
-    belongs_to :taxon, class_name: "Spree::Taxon", optional: true
+    belongs_to :condition, class_name: "SolidusPromotions::Condition"
+    belongs_to :taxon, class_name: "Spree::Taxon"
   end
 end

promotions/app/models/solidus_promotions/condition_user.rb

@@ -2,7 +2,7 @@
 
 module SolidusPromotions
   class ConditionUser < Spree::Base
-    belongs_to :condition, class_name: "SolidusPromotions::Condition", optional: true
-    belongs_to :user, class_name: Spree::UserClassHandle.new, optional: true
+    belongs_to :condition, class_name: "SolidusPromotions::Condition"
+    belongs_to :user, class_name: Spree::UserClassHandle.new
   end
 end