/api/orders/{orderId}/status

public class OrderStatusController : ApiController
{
    private readonly IOrderStatusApiService _apiService;

    public OrderStatusController(IOrderStatusApiService apiService)
    {
        _apiService = apiService;
    }

    public OrderStatusModel Get(int orderId)
    {
        return _apiService.Get(orderId);
    }

    public OrderStatusModel Put(int orderId, [FromBody]OrderStatusModel orderStatus)
    {
        return _apiService.Update(orderId, orderStatus);
    }
}

public class OrderStatusModel
{
    public string Note { get; set; }

    public OrderStatusEnum Status { get; set; }

    public DateTime TimeStamp { get; set; }

    public string ChangedBy { get; set; }
}

public enum OrderStatusEnum
{
    Requested = 1,

    Processing = 2,

    //... others

    Done = 99
}

public interface IOrderStatusApiService
{
    OrderStatusModel Get(int orderId);

    OrderStatusModel Update(int orderId, OrderStatusModel orderStatus);
}

public class OrderStatusApiService : IOrderStatusApiService
{
    private readonly IOrderStatusAppService _appService;

    public OrderStatusApiService(IOrderStatusAppService appService)
    {
        _appService = appService;
    }

    public OrderStatusModel Get(int orderId)
    {
        return _appService.Get(orderId).ToResourceModel();
    }

    public OrderStatusModel Update(int orderId, OrderStatusModel order)
    {
        var currentState = _appService.Get(orderId).ToResourceModel();

        if (currentState.Status != order.Status)
        {
            return _appService
                .UpdateStatus(orderId, (OrderStatusEnumDto)order.Status, order.Note)
                .ToResourceModel();
        }

        return currentState;
    }
}

public interface IOrderStatusAppService
{
    OrderStatusDto Get(int orderId);

    OrderStatusDto UpdateStatus(int orderId, OrderStatusEnum orderStatusStatus, string orderStatusNote);
}

public static class OrderStatusExtensions
{
    public static OrderStatusModel ToResourceModel(this OrderStatusDto dto)
    {
        return new OrderStatusModel()
                   {
                       ChangedBy = dto.ChangedBy,
                       Note = dto.Note,
                       Status = dto.Status,
                       TimeStamp = dto.TimeStamp
                   };
    }
}

public class OrderStatusDto
{
    public string Note { get; set; }

    public OrderStatusEnumDto Status { get; set; }

    public DateTime TimeStamp { get; set; }

    public string ChangedBy { get; set; }
}

public enum OrderStatusEnumDto
{
    Requested = 1,

    Processing = 2,

    //... others

    Done = 99
}