Sync refactor — Part 1 (#1688)

* It's half-alive

* Wakeups largely working

* Other tweaks, typing works

* Fix bugs, add receipt stream

* Delete notifier, other tweaks

* Dedupe a bit, add a template for the invite stream

* Clean up, add templates for other streams

* Don't leak channels

* Bring forward some more PDU logic, clean up other places

* Add some more wakeups

* Use addRoomDeltaToResponse

* Log tweaks, typing fixed?

* Fix timed out syncs

* Don't reset next batch position on timeout

* Add account data stream/position

* End of day

* Fix complete sync for receipt, typing

* Streams package

* Clean up a bit

* Complete sync send-to-device

* Don't drop errors

* More lightweight notifications

* Fix typing positions

* Don't advance position on remove again unless needed

* Device list updates

* Advance account data position

* Use limit for incremental sync

* Limit fixes, amongst other things

* Remove some fmt.Println

* Tweaks

* Re-add notifier

* Fix invite position

* Fixes

* Notify account data without advancing PDU position in notifier

* Apply account data position

* Get initial position for account data

* Fix position update

* Fix complete sync positions

* Review comments @Kegsay

* Room consumer parameters

syncapi/streams/template_pstream.go

@@ -0,0 +1,38 @@
+package streams
+
+import (
+	"context"
+	"sync"
+
+	"github.com/matrix-org/dendrite/syncapi/storage"
+	"github.com/matrix-org/dendrite/syncapi/types"
+)
+
+type PartitionedStreamProvider struct {
+	DB          storage.Database
+	latest      types.LogPosition
+	latestMutex sync.RWMutex
+}
+
+func (p *PartitionedStreamProvider) Setup() {
+}
+
+func (p *PartitionedStreamProvider) Advance(
+	latest types.LogPosition,
+) {
+	p.latestMutex.Lock()
+	defer p.latestMutex.Unlock()
+
+	if latest.IsAfter(&p.latest) {
+		p.latest = latest
+	}
+}
+
+func (p *PartitionedStreamProvider) LatestPosition(
+	ctx context.Context,
+) types.LogPosition {
+	p.latestMutex.RLock()
+	defer p.latestMutex.RUnlock()
+
+	return p.latest
+}