|Unique ID for every bid request in the system. A joining key for all the events associated with the bid request, like impression, clicks, and activities.
|Device ID for mobile, cookie for desktop. Will populate with cookie on a desktop OR an iOS/Android ID for mobile
|GDPR-compliant hashed user_id
|AIDEM segment ID; contains all segments the user qualifies for, comma-delimited, regardless if it is targeted on the line item that won
|The length of this field is unbounded since there can be many segment IDs that a user qualifies for