Add some roomserver UTs (#3067)

Adds tests for `QueryRestrictedJoinAllowed`, `IsServerAllowed` and
`PerformRoomUpgrade`. Refactors the `QueryRoomVersionForRoom` method to
accept a string and return a `gmsl.RoomVersion` instead of req/resp
structs.
Adds some more caching for `GetStateEvent`

This should also fix #2912 by ignoring state events belonging to other
users.

federationapi/routing/peek.go

@@ -35,10 +35,8 @@ func Peek(
 	remoteVersions []gomatrixserverlib.RoomVersion,
 ) util.JSONResponse {
 	// TODO: check if we're just refreshing an existing peek by querying the federationapi
-
-	verReq := api.QueryRoomVersionForRoomRequest{RoomID: roomID}
-	verRes := api.QueryRoomVersionForRoomResponse{}
-	if err := rsAPI.QueryRoomVersionForRoom(httpReq.Context(), &verReq, &verRes); err != nil {
+	roomVersion, err := rsAPI.QueryRoomVersionForRoom(httpReq.Context(), roomID)
+	if err != nil {
 		return util.JSONResponse{
 			Code: http.StatusInternalServerError,
 			JSON: jsonerror.InternalServerError(),
@@ -50,7 +48,7 @@ func Peek(
 	// the peek URL.
 	remoteSupportsVersion := false
 	for _, v := range remoteVersions {
-		if v == verRes.RoomVersion {
+		if v == roomVersion {
 			remoteSupportsVersion = true
 			break
 		}
@@ -59,7 +57,7 @@ func Peek(
 	if !remoteSupportsVersion {
 		return util.JSONResponse{
 			Code: http.StatusBadRequest,
-			JSON: jsonerror.IncompatibleRoomVersion(verRes.RoomVersion),
+			JSON: jsonerror.IncompatibleRoomVersion(roomVersion),
 		}
 	}
 
@@ -69,7 +67,7 @@ func Peek(
 	renewalInterval := int64(60 * 60 * 1000 * 1000)
 
 	var response api.PerformInboundPeekResponse
-	err := rsAPI.PerformInboundPeek(
+	err = rsAPI.PerformInboundPeek(
 		httpReq.Context(),
 		&api.PerformInboundPeekRequest{
 			RoomID:          roomID,