Preparations to actually remove/replace `BaseDendrite`.
Quite a few changes:
- SyncAPI accepts an `fulltext.Indexer` interface (fulltext is removed
from `BaseDendrite`)
- Caches are removed from `BaseDendrite`
- Introduces a `Router` struct (likely to change)
- also fixes#2903
- Introduces a `sqlutil.ConnectionManager`, which should remove
`base.DatabaseConnection` later on
- probably more
* Update GMSL
* Add MSC2836EventRelationships to fedsender
* Call MSC2836EventRelationships in reqCtx
* auth remote servers
* Extract room ID and servers from previous events; refactor a bit
* initial cut of federated threading
* Use the right client/fed struct in the response
* Add QueryAuthChain for use with MSC2836
* Add auth chain to federated response
* Fix pointers
* under CI: more logging and enable mscs, nil fix
* Handle direction: up
* Actually send message events to the roomserver..
* Add children and children_hash to unsigned, with tests
* Add logic for exploring threads and tracking children; missing storage functions
* Implement storage functions for children
* Add fetchUnknownEvent
* Do federated hits for include_children if we have unexplored children
* Use /ev_rel rather than /event as the former includes child metadata
* Remove cross-room threading impl
* Enable MSC2836 in the p2p demo
* Namespace mscs db
* Enable msc2836 for ygg
Co-authored-by: Neil Alexander <neilalexander@users.noreply.github.com>
