IWithId

A marker interface for entities that have a Guid identifier. It's deliberately minimal — something you can check for, dispatch on, or constrain generics against, without pulling in a heavier domain abstraction.

public interface IWithId
{
    Guid Id { get; }
}

Usage

using Servus;

public class Order : IWithId
{
    public Guid Id { get; init; } = Guid.NewGuid();
    // …
}

public void Log<T>(T entity) where T : IWithId
    => logger.LogInformation("Processed {Type} {Id}", typeof(T).Name, entity.Id);

Combine with InvokeIf to check for identifiability at runtime:

message.InvokeIf<IWithId>(e => diagnostics.Attach("entity.id", e.Id));