consolidate shared helpers into utils crate

crates/signed_core/src/inbox.rs

@@ -188,8 +188,8 @@ where
         .map(|root| {
             let mut events = groups.remove(&root).unwrap_or_default();
             let mut own_events = own_groups.remove(&root).unwrap_or_default();
-            sort_newest_first(&mut events);
-            sort_newest_first(&mut own_events);
+            utils::sort_newest_first(&mut events);
+            utils::sort_newest_first(&mut own_events);
 
             let root_event = lookup(root);
 
@@ -218,15 +218,6 @@ where
     items
 }
 
-/// Sort thread events newest first, ties broken by id.
-fn sort_newest_first(events: &mut [Event]) {
-    events.sort_by(|a, b| {
-        b.created_at
-            .cmp(&a.created_at)
-            .then_with(|| b.id.to_hex().cmp(&a.id.to_hex()))
-    });
-}
-
 /// Read and archive state of the inbox, a high-water-mark model.
 #[derive(Clone, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
 pub struct InboxReadState {