feat: automatically remove queued messages with stale locks (#2872)

doc/config/yaml.yml

@@ -29,6 +29,8 @@ postal:
   smtp_relays: []
   # An array of IP addresses to trust for proxying requests to Postal (in addition to localhost addresses)
   trusted_proxies: []
+  # The number of days after which to consider a lock as stale. Messages with stale locks will be removed and not retried.
+  queued_message_lock_stale_days: 1
 
 web_server:
   # The default port the web server should listen on unless overriden by the PORT environment variable