Make postgres::Client Send again

Closes #677

postgres/src/connection.rs

@@ -16,14 +16,14 @@ pub struct Connection {
     runtime: Runtime,
     connection: Pin<Box<dyn Stream<Item = Result<AsyncMessage, Error>> + Send>>,
     notifications: VecDeque<Notification>,
-    notice_callback: Arc<dyn Fn(DbError)>,
+    notice_callback: Arc<dyn Fn(DbError) + Sync + Send>,
 }
 
 impl Connection {
     pub fn new<S, T>(
         runtime: Runtime,
         connection: tokio_postgres::Connection<S, T>,
-        notice_callback: Arc<dyn Fn(DbError)>,
+        notice_callback: Arc<dyn Fn(DbError) + Sync + Send>,
     ) -> Connection
     where
         S: AsyncRead + AsyncWrite + Unpin + 'static + Send,

postgres/src/test.rs

@@ -499,3 +499,12 @@ fn explicit_close() {
     let client = Client::connect("host=localhost port=5433 user=postgres", NoTls).unwrap();
     client.close().unwrap();
 }
+
+#[test]
+fn check_send() {
+    fn is_send<T: Send>() {}
+
+    is_send::<Client>();
+    is_send::<Statement>();
+    is_send::<Transaction<'_>>();
+}