Utf8Json - сериализация перечислений из числа в строку

[DataContract]
public class Physics
{
    [DataMember]
    public string Lecturer { get; set; }
 
    [DataMember]
    public WeekDays WeekDay { get; set; }
}
 
[DataContract]
public enum WeekDays : byte
{
    [EnumMember]
    Monday = 1,
 
    [EnumMember]
    Tuesday,
 
    [EnumMember]
    Wednesday,
 
    [EnumMember]
    Thursday,
 
    [EnumMember]
    Friday,
 
    [EnumMember]
    Saturday,
 
    [EnumMember]
    Sunday
}

static void Main(string[] args)
    {
        Physics physics_1 = new Physics { Lecturer = "Andrew", WeekDay = WeekDays.Monday };
        var v1 = JsonSerializer.Serialize(physics_1, EnumResolver.UnderlyingValue);
        Console.WriteLine(Encoding.UTF8.GetString(v1));
    }

using System;
using System.Text;
 
using Utf8Json;
using Utf8Json.Resolvers;
 
CompositeResolver.RegisterAndSetAsDefault(
    new IJsonFormatter[] { new WeekDaysFormatter() },
    new[] { StandardResolver.Default });
 
Physics physics_1 = new Physics { Lecturer = "Andrew", WeekDay = WeekDays.Monday };
var v1 = JsonSerializer.Serialize(physics_1);
Console.WriteLine(Encoding.UTF8.GetString(v1));
 
public sealed class WeekDaysFormatter : IJsonFormatter<WeekDays>
{
    public void Serialize(ref JsonWriter writer, WeekDays value, IJsonFormatterResolver formatterResolver)
    {
        writer.WriteByte((byte)value);
    }
 
    public WeekDays Deserialize(ref JsonReader reader, IJsonFormatterResolver formatterResolver)
        => throw new NotImplementedException();
}
 
public class Physics
{
    public string Lecturer { get; set; }
    public WeekDays WeekDay { get; set; }
}
 
public enum WeekDays : byte
{
    Monday = 1,
    Tuesday,
    Wednesday,
    Thursday,
    Friday,
    Saturday,
    Sunday
}

CompositeResolver.RegisterAndSetAsDefault(
    //new IJsonFormatter[] { new WeekDaysFormatter() },
    new[] { EnumResolver.UnderlyingValue, StandardResolver.Default });