Fixes the mandrill's silent discard of cc.

mandrill.php

/**
 * Fixes the mandrill's silent discard of cc.
 */
//first add filter to EE's email process to modify `cc:` header to `x-cc` so it gets past the initial mandrill header setup.
add_filter('FHEE__EE_Email_messenger___headers', function($headers) {
    foreach ($headers as $header) {
        if (strpos($header, 'cc: ') !== false) {
            $headers[] = 'x-cc: ' . str_replace('cc: ', '', $header);
        }
    }
    return $headers;
}, 5);
//next capture the x-cc from the header and add it to the `to` array (with type set as 'cc') then remove the special
// `x-cc` header.
add_filter('mandrill_payload', function($payload){
    if (isset($payload['headers'], $payload['headers']['x-cc'])) {
        $cc_emails = $payload['headers']['x-cc'];
        unset($payload['headers']['x-cc']);
        $cc_emails = explode(',', $cc_emails);
        $cc_emails = array_map('trim', $cc_emails);
        foreach($cc_emails as $cc) {
            $payload['to'][] = array(
                'email' => $cc,
                'type' => 'cc'
            );
        }
    }
    return $payload;
});