Add functionality to order insufficient supplies for plan templates.

Models/Supply/SupplyAvailability.cs

@@ -0,0 +1,11 @@
+namespace CarCareTracker.Models
+{
+    public class SupplyAvailability
+    {
+        public bool Missing { get; set; }
+        public string Description { get; set; } = string.Empty;
+        public decimal Required { get; set; }
+        public decimal InStock { get; set; }
+        public bool Insufficient { get { return Required > InStock; } }
+    }
+}