upload: Allow rate limited access to spectators for uploaded files.

We allow spectators access to uploaded files in web public streams
but rate limit the daily requests to 1000 per file by default.

zproject/computed_settings.py

@@ -394,6 +394,9 @@ RATE_LIMITING_RULES = {
     "sends_email_by_ip": [
         (86400, 5),
     ],
+    "spectator_attachment_access_by_file": [
+        (86400, 1000),  # 1000 per day per file
+    ],
 }
 
 # List of domains that, when applied to a request in a Tornado process,