embedded bots: Run bot.initialize() if bot has this function.

zerver/worker/queue_processors.py

@@ -531,6 +531,8 @@ class EmbeddedBotWorker(QueueProcessingWorker):
                 logging.error("Error: User %s has bot with invalid embedded bot service %s" % (
                     user_profile_id, service.name))
                 continue
+            if hasattr(bot_handler, 'initialize'):
+                bot_handler.initialize(self.get_bot_api_client(user_profile))
             if event['trigger'] == 'mention':
                 message['content'] = extract_query_without_mention(
                     message=message,