make thread safe connection more thread safe

Co-Authored-By: Mikayla Maki <mikayla@zed.dev>

crates/sqlez/src/util.rs

@@ -4,6 +4,10 @@ use std::sync::mpsc::Sender;
 use parking_lot::Mutex;
 use thread_local::ThreadLocal;
 
+/// Unbounded standard library sender which is stored per thread to get around
+/// the lack of sync on the standard library version while still being unbounded
+/// Note: this locks on the cloneable sender, but its done once per thread, so it
+/// shouldn't result in too much contention
 pub struct UnboundedSyncSender<T: Send> {
     clonable_sender: Mutex<Sender<T>>,
     local_senders: ThreadLocal<Sender<T>>,