lib/authorizer/digest.js
function _getDigestAuthHeader (headers) {
    return headers.find(function (property) {
        return (property.key.toLowerCase() === WWW_AUTHENTICATE) && (_.startsWith(property.value, DIGEST_PREFIX));
    });
}
function _getDigestAuthHeader (headers) {
    return headers.find(function (property) {
        return (property.key.toLowerCase() === WWW_AUTHENTICATE) && (_.startsWith(property.value, DIGEST_PREFIX));
    });
}
function _getDigestAuthHeader ( headers ) { return headers . find ( function ( property ) { return ( property . key . toLowerCase ( ) === WWW_AUTHENTICATE ) && ( _ . startsWith ( property . value , DIGEST_PREFIX ) ) ; } ) ; }
Returns the 'www-authenticate' header for Digest auth. Since a server can suport more than more auth-scheme,
there can be more than one header with the same key. So need to loop over and check each one.

@param {VariableList} headers
@private
Returns the www - authenticate header for Digest auth . Since a server can suport more than more auth - scheme there can be more than one header with the same key . So need to loop over and check each one .