Cleanroom details for template APIs. For create (CreateCleanRoomTemplate), required fields are name and type; ownerAccount is required when type is Snowflake. startAt is set server-side to today (yyyy-mm-dd) and is ignored if provided. organizationID and isTemplate are set server-side. For update, name and type are required; startAt is preserved from the existing template. For instantiate (CloneCleanRoom), only name is required; startAt is inherited from the source template.