// 1) Get the CURRENT joined room list for this user
// 2) Get membership list changes for this user between the provided stream position and now.
// 3) For each room which has membership list changes:
// a) Check if the room is 'newly joined' (insufficient to just check for a join event because we allow dupe joins).
// If it is, then we need to send the full room state down (and 'limited' is always true).
// b) Check if user is still CURRENTLY invited to the room. If so, add room to 'invited' block.
// c) Check if the user is CURRENTLY left/banned. If so, add room to 'archived' block. // Synapse has a TODO: How do we handle ban -> leave in same batch?