Apply suggestions from code review

Co-authored-by: Paul Wilson <[email protected]>
Signed-off-by: Katie Mummah <[email protected]>

src/material.h

@@ -160,7 +160,7 @@ class Material: public Resource {
   virtual void ChangePackageId(int new_package_id);
 
  protected:
-  Material(Context* ctx, double quantity, Composition::Ptr c, int package_id = 1);
+  Material(Context* ctx, double quantity, Composition::Ptr c, int package_id = default_package_id_);
 
  private:
   Context* ctx_;

src/product.h

@@ -28,7 +28,7 @@ class Product : public Resource {
   /// pointer to the agent creating the resource (usually will be the caller's
   /// "this" pointer). All future output data recorded will be done using the
   /// creator's context.
-  static Ptr Create(Agent* creator, double quantity, std::string quality, int package_id = 1);
+  static Ptr Create(Agent* creator, double quantity, std::string quality, int package_id = default_package_id_);
 
   /// Creates a new product that does not actually exist as part of
   /// the simulation and is untracked.
@@ -75,7 +75,7 @@ class Product : public Resource {
   /// @param ctx the simulation context
   /// @param quantity is a double indicating the quantity
   /// @param quality the resource quality
-  Product(Context* ctx, double quantity, std::string quality, int package_id = 1);
+  Product(Context* ctx, double quantity, std::string quality, int package_id = default_package_id_);
 
   // map<quality, quality_id>
   static std::map<std::string, int> qualids_;