Asset
- urlType: stringFormat: urirequired
- expiresType: stringFormat: date-time
_at the date-time notation as defined by RFC 3339, section 5.6, for example, 2017-07-21T17:32:28Z
the date-time notation as defined by RFC 3339, section 5.6, for example, 2017-07-21T17:32:28Z