fix: some compile time errors

Only 174 errors left!

src/service/rooms/auth_chain/data.rs

@@ -1,3 +1,5 @@
+use std::collections::HashSet;
+
 pub trait Data {
     fn get_cached_eventid_authchain<'a>() -> Result<HashSet<u64>>;
     fn cache_eventid_authchain<'a>(shorteventid: u64, auth_chain: &HashSet<u64>) -> Result<HashSet<u64>>;