Added login/register function. Implemented authentication. Started authorization

Moonlight.ApiServer/Database/Entities/User.cs

@@ -0,0 +1,13 @@
+namespace Moonlight.ApiServer.Database.Entities;
+
+public class User
+{
+    public int Id { get; set; }
+
+    public string Username { get; set; }
+    public string Email { get; set; }
+    public string Password { get; set; }
+
+    public DateTime TokenValidTimestamp { get; set; } = DateTime.UtcNow;
+    public string PermissionsJson { get; set; } = "[]";
+}