Address review issues, fix forward extremity calc

Keep track of all prev_events since if we know that an event is a
prev_event it is referenced and does not qualify as a forward extremity.

src/database/globals.rs

@@ -27,7 +27,11 @@ pub struct Globals {
 }
 
 impl Globals {
-    pub fn load(globals: sled::Tree, server_keys: sled::Tree, config: Config) -> Result<Self> {
+    pub fn load(
+        globals: sled::Tree,
+        servertimeout_signingkey: sled::Tree,
+        config: Config,
+    ) -> Result<Self> {
         let bytes = &*globals
             .update_and_fetch("keypair", utils::generate_keypair)?
             .expect("utils::generate_keypair always returns Some");
@@ -84,7 +88,7 @@ impl Globals {
             })?,
             actual_destination_cache: Arc::new(RwLock::new(HashMap::new())),
             jwt_decoding_key,
-            servertimeout_signingkey: server_keys,
+            servertimeout_signingkey,
         })
     }