FIX: Ensure valid json (#39)

* Build EVENT message with json.dumps instead of string interpolation

Ensures outbound Nostr messages are valid JSON and safely escaped by
constructing the payload as Python objects and serializing with
json.dumps

* improve logs

* remove log causing check failure

router.py

@@ -111,10 +111,14 @@ class NostrRouter:
                 # this reconstructs the original response from the relay
                 # reconstruct original subscription id
                 s_original = self.original_subscription_ids[s]
-                event_to_forward = f"""["EVENT", "{s_original}", {event_json}]"""
+                event_to_forward = json.dumps(
+                    ["EVENT", s_original, json.loads(event_json)]
+                )
                 await self.websocket.send_text(event_to_forward)
         except Exception as e:
-            logger.debug(e)  # there are 2900 errors here
+            logger.warning(
+                f"[NOSTRCLIENT] Error in _handle_received_subscription_events: {e}"
+            )
 
     def _handle_notices(self):
         while len(NostrRouter.received_subscription_notices):