How to do a Facebook OAuth Login for HANA XS App in Trial Account?

Currently I am playing around with Facebook logins from the SAP HCP Trial account.

Using the Facebook JavaScript SDK in an HTML5 app works easily with a few lines of code.

Now I try to do it in an XS application. I found this blog about OAuth2 Authentication but this does not seem to work in the Trial landscape?

I also read the blog from Chris Paine or Chris Paine but there is also Java code involved and maybe things changed in the last two years?

Then I read many help pages from SAP HCP help about OAuth, Trust etc but the more I read the more I am confused

So my question is:

How can I do a Facebook login via OAuth in an HANA XS app on the trial landscape?

Any hints or tips for further steps appreciated

Thank you for your help,

Mark