Move support for application service query parameter authorization behind a configuration option (#16017)

docs/usage/configuration/config_documentation.md

@@ -2848,6 +2848,20 @@ Example configuration:
 ```yaml
 track_appservice_user_ips: true
 ```
+---
+### `use_appservice_legacy_authorization`
+
+Whether to send the application service access tokens via the `access_token` query parameter
+per older versions of the Matrix specification. Defaults to false. Set to true to enable sending
+access tokens via a query parameter.
+
+**Enabling this option is considered insecure and is not recommended. **
+
+Example configuration:
+```yaml
+use_appservice_legacy_authorization: true 
+```
+
 ---
 ### `macaroon_secret_key`