Add an optional flag to the PostDocument endpoint to skip auto tagging

docs/api.md

@@ -192,6 +192,8 @@ The endpoint supports the following optional form fields:
 -   `tags`: Similar to correspondent. Specify this multiple times to
     have multiple tags added to the document.
 -   `archive_serial_number`: An optional archive serial number to set.
+-   `skip_auto_tags`: Boolean to indicate that the classifier should not
+    attempt to determine and add tags to the document.
 -   `custom_fields`: An array of custom field ids to assign (with an empty
     value) to the document.