The channel the group is on — the same value its messages carry. Never changes.
ISO-8601: when Dial first learned of this group (your line being added to it, or its first message) — not when the group itself was created.
The group's Dial id. Pass it as groupId when sending or listing.
The group's current name, or null when no line could report it in time.
Not stored by Dial: participants rename groups, so it's read live from the line holding the conversation. A line that can't answer yields null here rather than failing the whole listing — retry if you need the name.
A group conversation — a conversation that isn't a phone number, so it carries an id of its own.