wip maybe

wp_remote_post files

$response = wp_remote_post( 
    "https://api.freewheel.tv/services/upload/bvi.xml", 
    array(
        'method' => 'POST',
        'timeout' => 30,
        'redirection' => 5,
        'httpversion' => '1.0',
        'headers' => array(
            'X-FreeWheelToken' => 'MYAPIKEY',
            'Expect' => ????
        ),
        'body' => array('post_file'=>'@/my_file1.xml'),
        'sslverify' => false
    )
);