fix: Listener retries should be performed with exceptions unmasked

forkFinally calls error handler with exceptions masked. Our handleFinally does not restore exception state before calling retryingListener so after first error the whole listener is running with exceptions masked.
This patch ensures handleFinally is run with exceptions unmasked.

Author: mkleczek

src/PostgREST/Listener.hs

@@ -44,9 +44,11 @@ retryingListen appState = do
       unless (delay == maxDelay) $
         AppState.putNextListenerDelay appState (delay * 2)
       retryingListen appState
+    
+    withHandler action = mask $ \restore -> forkIO $ try (restore action) >>= restore . handleFinally
 
   -- forkFinally allows to detect if the thread dies
-  void . flip forkFinally handleFinally $ do
+  void . withHandler $ do
     bracket (SQL.acquire $ toUtf8 (Config.addTargetSessionAttrs $ Config.addFallbackAppName prettyVersion configDbUri)) (`whenRight` releaseConnection) $ \dbOrError -> do
       case dbOrError of
         Right db -> do