Added authenication/authorization. Refactored api startup.

JSMR.Domain/Entities/User.cs

@@ -0,0 +1,10 @@
+namespace JSMR.Domain.Entities;
+
+public class User
+{
+    public int Id { get; set; }
+    public string Username { get; set; } = string.Empty;
+    public string PasswordHash { get; set; } = string.Empty;
+    public string? Role { get; set; }
+    public bool IsActive { get; set; } = true;
+}