Fixes a variety of issues where clients were receiving pseudoIDs in
places that should be userIDs.
This change makes pseudoIDs work with sliding sync & element x.
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Co-authored-by: Till <2353100+S7evinK@users.noreply.github.com>
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
