Support for Bearer token authentication

[mcquaas]

Restful requests can currently be made sending the token via a simple "Authentication: {your_token}" header.

But many applications, including Postman and OpenApi compliant integrations expect the token to be sent in the form of: "Authentication: Bearer {your_token}".

A simple add-on to the get_wstoken($headers) can do the work:

private function get_wstoken($headers) {
    $wstoken = '';

    if (isset($headers['HTTP_AUTHORIZATION'])) {
        $authorizationHeader = $headers['HTTP_AUTHORIZATION'];
        $authorizationHeaderParts = explode(' ', $authorizationHeader);
        if (count($authorizationHeaderParts) === 2 && $authorizationHeaderParts[0] === 'Bearer') {
            $wstoken = $authorizationHeaderParts[1];
        } else {
            $wstoken = $authorizationHeader;
        }
    }

    if ($wstoken === '') {
        // Raise an error if auth header not supplied.
        $ex = new \moodle_exception('noauthheader', 'webservice_restful', '');
        $this->send_error($ex, 401);
    }

    return $wstoken;
}

Hope this helps.