For each successful request of a group profile, we previously
emitted an `updateGroupProfile` event per caller of
`getGroupProfileCached`. This is sub-optimal because only a single
event emit is required to update the views listening.
It's possible that this was enabling some race to cause a memory
leak but this is not certain, hence the extra logging for future
debugging.
Also, delete the groupProfilePromise immediately after setting
the group profile (the first if-statement will prevent a new
request from being started).
Previously, a single user could end up in multiple batches, which would have been fine if the logic didn't assume otherwise. If a request took longer than 200ms, multiple batches would occur with intersecting sets of users, deleting promises that were then assumed to exist.
The logic now takes all "in flight" users to also not be "pending". Pending now means that the user will be processed in the next batch. "In flight" means the user is part of an ongoing batch.
This will make invalidating the userGroups cache for the user architecturally more sound (the plan is to have GroupStore hit FlairStore as opposed to Flair itself in order to invalidate the cache).
