Optional properties:
allocation
:<string>
- Media set allocation policy ('continue', 'always', or a calendar event).
comment
:<string>
- Comment (single line).
encrypt
:<string>
- Tape encryption key fingerprint (sha256).
retention
:<string>
- Media retention policy ('overwrite', 'keep', or time span).
template
:<string>
- Media set naming template (may contain strftime() time format specifications).