Update data access layer, begin acquiring raw data

DataAccessLayer/IRepository.cs

@@ -0,0 +1,14 @@
+using System;
+using System.Collections.Generic;
+
+namespace DataAccessLayer
+{
+    public interface IRepository<T>
+        where T : class
+    {
+        void Add(T entity);
+        T? GetById(Guid id);
+        void Update(T entity);
+        void Delete(Guid id);
+    }
+}