google-calendar: Use a bot to send direct messages to the bot owner.

The reminders were previously being sent to the DMs of the current user,
requiring the zuliprc of the user.
But, we can create a generic bot for the Google Calendar integration,
and use its zuliprc to send direct messages to its owner. This tightens
security.

The support for sending DMs to the same user is retained, for cases
where a bot is not used.

Author: Niloth-p

zulip/integrations/google/google-calendar

@@ -29,13 +29,12 @@ sent: Set[Tuple[int, datetime.datetime]] = set()
 
 sys.path.append(os.path.dirname(__file__))
 
-usage = r"""google-calendar [--interval MINUTES] [--calendar CALENDAR_ID]
+usage = r"""google-calendar [--config-file PATH_TO_ZULIPRC_OF_BOT]
+                       [--interval MINUTES] [--calendar CALENDAR_ID]
 
     This integration can be used to send Zulip messages as reminders for upcoming events from your Google Calendar.
 
-    Specify your Zulip API credentials and server in a ~/.zuliprc file, or using the options.
-
-    This integration should be run on your local machine, as your API key is accessible to local users through the command line.
+    Create a generic bot on Zulip, download its zuliprc file, and use the --config-file option to specify the path to your bot's zuliprc.
 
     For more information, see https://zulip.com/integrations/doc/google-calendar.
 """
@@ -162,8 +161,13 @@ def send_reminders() -> Optional[None]:
     else:
         message = "Reminder:\n\n" + "\n".join("* " + m for m in messages)
 
+    user_profile = zulip_client.get_profile()
     result = zulip_client.send_message(
-        {"type": "direct", "to": [zulip_client.get_profile()["email"]], "content": message}
+        {
+            "type": "direct",
+            "to": [user_profile.get("bot_owner_id") or user_profile["email"]],
+            "content": message,
+        }
     )
     if result["result"] != "success":
         logging.error("Error sending zulip message: %s: %s", result.get("code"), result.get("msg"))