de-MSC-ifying space summaries (MSC2946) (#3134)

- This PR moves and refactors the
[code](https://github.com/matrix-org/dendrite/blob/main/setup/mscs/msc2946/msc2946.go)
for
[MSC2946](https://github.com/matrix-org/matrix-spec-proposals/pull/2946)
('Space Summaries') to integrate it into the rest of the codebase.
- Means space summaries are no longer hidden behind an MSC flag
- Solves #3096

Signed-off-by: Sam Wedgwood <sam@wedgwood.dev>

internal/caching/cache_roomservernids.go

@@ -8,6 +8,7 @@ type RoomServerCaches interface {
 	RoomServerNIDsCache
 	RoomVersionCache
 	RoomServerEventsCache
+	RoomHierarchyCache
 	EventStateKeyCache
 	EventTypeCache
 }

internal/caching/cache_space_rooms.go

@@ -2,15 +2,16 @@ package caching
 
 import "github.com/matrix-org/gomatrixserverlib/fclient"
 
-type SpaceSummaryRoomsCache interface {
-	GetSpaceSummary(roomID string) (r fclient.MSC2946SpacesResponse, ok bool)
-	StoreSpaceSummary(roomID string, r fclient.MSC2946SpacesResponse)
+// RoomHierarchy cache caches responses to federated room hierarchy requests (A.K.A. 'space summaries')
+type RoomHierarchyCache interface {
+	GetRoomHierarchy(roomID string) (r fclient.RoomHierarchyResponse, ok bool)
+	StoreRoomHierarchy(roomID string, r fclient.RoomHierarchyResponse)
 }
 
-func (c Caches) GetSpaceSummary(roomID string) (r fclient.MSC2946SpacesResponse, ok bool) {
-	return c.SpaceSummaryRooms.Get(roomID)
+func (c Caches) GetRoomHierarchy(roomID string) (r fclient.RoomHierarchyResponse, ok bool) {
+	return c.RoomHierarchies.Get(roomID)
 }
 
-func (c Caches) StoreSpaceSummary(roomID string, r fclient.MSC2946SpacesResponse) {
-	c.SpaceSummaryRooms.Set(roomID, r)
+func (c Caches) StoreRoomHierarchy(roomID string, r fclient.RoomHierarchyResponse) {
+	c.RoomHierarchies.Set(roomID, r)
 }

internal/caching/caches.go

@@ -35,7 +35,7 @@ type Caches struct {
 	RoomServerEventTypes    Cache[types.EventTypeNID, string]                      // eventType NID -> eventType
 	FederationPDUs          Cache[int64, *types.HeaderedEvent]                     // queue NID -> PDU
 	FederationEDUs          Cache[int64, *gomatrixserverlib.EDU]                   // queue NID -> EDU
-	SpaceSummaryRooms       Cache[string, fclient.MSC2946SpacesResponse]           // room ID -> space response
+	RoomHierarchies         Cache[string, fclient.RoomHierarchyResponse]           // room ID -> space response
 	LazyLoading             Cache[lazyLoadingCacheKey, string]                     // composite key -> event ID
 }
 

internal/caching/impl_ristretto.go

@@ -147,7 +147,7 @@ func NewRistrettoCache(maxCost config.DataUnit, maxAge time.Duration, enableProm
 				MaxAge:  lesserOf(time.Hour/2, maxAge),
 			},
 		},
-		SpaceSummaryRooms: &RistrettoCachePartition[string, fclient.MSC2946SpacesResponse]{ // room ID -> space response
+		RoomHierarchies: &RistrettoCachePartition[string, fclient.RoomHierarchyResponse]{ // room ID -> space response
 			cache:   cache,
 			Prefix:  spaceSummaryRoomsCache,
 			Mutable: true,