Also fixes:
- Transaction IDs leaking in event route
- Age not being set for event relations or threads
- Both of the above for search results
Notes down concern with relations table
- Remove most usages of `update_membership` in favor
of directly calling the `mark_as_*` functions
- Store the leave membership event as the value in the
`userroomid_leftstate` table
- Use the `userroomid_leftstate` table to synchronize the
timeline and state for left rooms if possible
Jade Ellis
Ginger