Add project files.

ConstructorApp.EntityLayer/Entities/Reference.cs

@@ -0,0 +1,15 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace ConstructorApp.EntityLayer.Entities
+{
+    public class Reference
+    {
+        [Key]
+        public int ReferenceID { get; set; }
+        [StringLength(50)]
+        [Required]
+        public string? LogoUrl { get; set; }
+        [StringLength(50)]
+        public string? WebUrl { get; set; }
+    }
+}