ToJSON converts a Performer object into its JSON equivalent.

ValidateDeathDate returns an error if the birthdate is after the death date.

ValidateName returns an error if the performer name and disambiguation provided is used by another performer.

ValidateUpdateDeathDate performs the same check as ValidateDeathDate, but is used when modifying an existing performer.

ValidateUpdateName performs the same check as ValidateName, but is used when modifying an existing performer.