services.AddIdentity<IdentityUser, IdentityRole>(options => {
                options.Password.RequiredLength = 6;
                options.Password.RequireNonAlphanumeric = false;
                options.Password.RequireUppercase = false;
                options.User.RequireUniqueEmail = true;
            })
            .AddRoles<IdentityRole>()
            .AddRoleManager<RoleManager<IdentityRole>>()
            .AddDefaultUI()            
            .AddDefaultTokenProviders()
            .AddEntityFrameworkStores<ApplicationDbContext>();