Cleanup of lazy loading code. Made some DTOs use init rather than set to keep it clean.

API/Extensions/HttpExtensions.cs

@@ -1,4 +1,5 @@
-using System.Text.Json;
+using System.Linq;
+using System.Text.Json;
 using API.Helpers;
 using Microsoft.AspNetCore.Http;
 
@@ -18,6 +19,23 @@ namespace API.Extensions
             response.Headers.Add("Pagination", JsonSerializer.Serialize(paginationHeader, options));
             response.Headers.Add("Access-Control-Expose-Headers", "Pagination");
         }
+
+        /// <summary>
+        /// Calculates SHA1 hash for a byte[] and sets as ETag. Ensures Cache-Control: private header is added.
+        /// </summary>
+        /// <param name="response"></param>
+        /// <param name="content"></param>
+        public static void AddCacheHeader(this HttpResponse response, byte[] content)
+        {
+            // Calculates SHA1 Hash for byte[]
+            if (content != null && content.Length > 0)
+            {
+                using var sha1 = new System.Security.Cryptography.SHA1CryptoServiceProvider();
+                response.Headers.Add("ETag", string.Concat(sha1.ComputeHash(content).Select(x => x.ToString("X2"))));
+            }
+            
+            response.Headers.Add("Cache-Control", "private");
+        }
         
     }
 }