[friseurtermin]

One caveat here is serialization. Writing your (or another package's) enum to a database will get you in trouble if you ever want to add another value in the middle. Sure, you can be careful and should document this, but who knows

[Someone]

Not only that, but the person sending you the serialized object might be looking for trouble. Sending you an enum value that is outside the legal range might help an attacker get into your system.