how to create a jwt for an existing user in identity

  app.MapPost("/Security/Token/Create",
    [AllowAnonymous]
    async ([FromBody]WebAppMeet.Data.Models.UserTokenRequest user, [FromServices] SignInManager<AppUser> signInManager)
    =>
    {
        var appUser = await signInManager.UserManager.Users.FirstOrDefaultAsync(x => x.UserName == user.UserName);

        if ((await signInManager.PasswordSignInAsync(appUser, user.Password, true, false)).Succeeded)
        {
            var issuer = builder.Configuration["Jwt:Issuer"];
            var audience = builder.Configuration["Jwt:Audience"];
            var key = Encoding.ASCII.GetBytes(builder.Configuration["Jwt:Key"]);
            var tokenDescriptor = new SecurityTokenDescriptor
            {
                Subject = new ClaimsIdentity(new[]
                {
                    new Claim("Id", Guid.NewGuid().ToString()),
                    new Claim(JwtRegisteredClaimNames.Sub, user.UserName),
                    new Claim(JwtRegisteredClaimNames.Email, user.UserName),
                    new Claim(JwtRegisteredClaimNames.Jti,Guid.NewGuid().ToString())
                 }),
                Expires = DateTime.UtcNow.AddMinutes(5),
                Issuer = issuer,
                Audience = audience,
                SigningCredentials = new SigningCredentials(new SymmetricSecurityKey(key), SecurityAlgorithms.HmacSha512Signature)
            };
            var tokenHandler = new JwtSecurityTokenHandler();
            var token = tokenHandler.CreateToken(tokenDescriptor);
            var jwtToken = tokenHandler.WriteToken(token);
            var stringToken = tokenHandler.WriteToken(token);
            return Results.Ok(stringToken);
        }
        return Results.Unauthorized();
    });