public static IEnumerable <MessageAbstraction> AttachMessage(this IEnumerable <MessageAbstraction> messages,
MessageAbstraction otherMessage)
=> messages.Append(otherMessage);
public static IEnumerable <MessageAbstraction> AttachMessage(this MessageAbstraction message,
MessageAbstraction otherMessage) => new[] { message, otherMessage };
public static IEnumerable <MessageAbstraction> AttachMessages(this MessageAbstraction message,
IEnumerable <MessageAbstraction> otherMessages)
=> new[] { message }.AttachMessages(otherMessages);