Following RFC 6585 https://tools.ietf.org/html/rfc6585, there is a
status code for ‘too many requests’, which applies well to the nginx
limiting requests, and by extension to the module limiting connections.
Having in mind changing default values is somewhat tricky regarding
backwards compatibility, would it be a possible enhancement to change
default value of limit_req_status and limit_conn_status from 503 to 429?