Reformat UserName to Username, Added DAL with admin login method

DataAccessLayer/Database/Service/UserService.cs

@@ -0,0 +1,26 @@
+using pacMan.GameStuff;
+using pacMan.GameStuff.Items;
+
+namespace DAL.Database.Service;
+
+public class UserService
+{
+    private readonly List<Player> _users = new()
+    {
+        new Player
+        {
+            Username = "admin",
+            Colour = "red",
+            PacMan = new Character
+            {
+                Colour = "red",
+                Type = CharacterType.PacMan
+            }
+        }
+    };
+
+    public async Task<IPlayer?> Login(string username, string password)
+    {
+        return await Task.Run(() => _users.FirstOrDefault(x => x.Username == username && password == "admin"));
+    }
+}