Variable DirectThreadDetailsSchemaConst

What the thread details hub is opened with and keeps, a sum on whether the thread is a group: each kind holds only the facts that exist for it.

• A one-to-one thread names its peer, the thread's own user (users[0]), which the thread screen carries from its answer — one source for both ids: peer_user_id is the pk the sharing-info query sends and peer_user_fbid the Facebook-side id (fbid_v2, the inbox row's person) the profile-updates query sends (run-direct-feed-theme 92); the sharing-info answer carries neither. The peer is also the person the hub asks about when it comes back in front.
• A group names its first participant, lead_user_id: the person the hub asks GetUserSharingInfo about when it comes back in front (the 451 direct-actions-group 105 names the group's first member). It sends no profile updates, so it holds no Facebook-side id.