rds_json_errcode_key will not echo anything while success query.

[xiaohuilam]

rds_json_errcode_key will not echo anything if query success.
some ajax program js front usually need a "code" result, so i find rds_json_errcode_key directive,
tested it and knew that it only work while query error. so could there any way to echo excution code?

[agentzh]

@xiaohuilam then we'll also need a rds_json_result_key directive. When it is on, we can always add the errcode key to the top-level JSON object. Patches welcome :)