Show all joinable rooms in the spaces summary. (#10298)

Previously only world-readable rooms were shown. This means that
rooms which are public, knockable, or invite-only with a pending invitation,
are included in a space summary. It also applies the same logic to
the experimental room version from MSC3083 -- if a user has access
to the proper allowed rooms then it is shown in the spaces summary.

This change is made per MSC3173 allowing stripped state of a room to
be shown to any potential room joiner.

synapse/storage/databases/main/roommember.py

@@ -703,13 +703,22 @@ class RoomMemberWorkerStore(EventsWorkerStore):
 
     @cached(max_entries=10000)
     async def is_host_joined(self, room_id: str, host: str) -> bool:
+        return await self._check_host_room_membership(room_id, host, Membership.JOIN)
+
+    @cached(max_entries=10000)
+    async def is_host_invited(self, room_id: str, host: str) -> bool:
+        return await self._check_host_room_membership(room_id, host, Membership.INVITE)
+
+    async def _check_host_room_membership(
+        self, room_id: str, host: str, membership: str
+    ) -> bool:
         if "%" in host or "_" in host:
             raise Exception("Invalid host name")
 
         sql = """
             SELECT state_key FROM current_state_events AS c
             INNER JOIN room_memberships AS m USING (event_id)
-            WHERE m.membership = 'join'
+            WHERE m.membership = ?
                 AND type = 'm.room.member'
                 AND c.room_id = ?
                 AND state_key LIKE ?
@@ -722,7 +731,7 @@ class RoomMemberWorkerStore(EventsWorkerStore):
         like_clause = "%:" + host
 
         rows = await self.db_pool.execute(
-            "is_host_joined", None, sql, room_id, like_clause
+            "is_host_joined", None, sql, membership, room_id, like_clause
         )
 
         if not rows: