Allows for alternate auth mode

[gms8994]

We're using a generated token from the Azure system instead of Oauth via a user. Minor difference is that now you

use ProcessMaker\Flysystem\Adapter\MSGraphApp as SharepointAdapter;

new SharepointAdapter(SharepointAdapter::MODE_SHAREPOINT, $sharepoint_site_id, $document_library, $access_token)

or

use ProcessMaker\Flysystem\Adapter\MSGraphUser as SharepointAdapter;

new SharepointAdapter($appId, $appPassword, $tokenEndpoint, SharepointAdapter::MODE_SHAREPOINT, $sharepoint_site_id, $document_library)

Feedback welcome.