Missing required key in single structure: user For auth_userkey_request_login_url

Hi All,

I am using auth_userkey_request_login_url  plugin to login with username.

I have developed angular App. 

Using Angular Service I am trying to call auth user key request to login url but it showing me following error.

<?xml version="1.0" encoding="UTF-8" ?>
<EXCEPTION class="invalid_parameter_exception">
    <ERRORCODE>invalidparameter</ERRORCODE>
    <MESSAGE>Invalid parameter value detected (Missing required key in single structure: user)</MESSAGE>
    <DEBUGINFO>Missing required key in single structure: user</DEBUGINFO>
</EXCEPTION>

Please help me for this.