The only usage for your facebook authentication data will be the convenience of identifying yourself with your facebook credentials to the platform
Such identification serves only the purpose of allowing for the generation of personalized feedback information regarding your services contracted with demian.app
Facebook authentication is only an option to engage in such personalization, as alternatives will be proviced when creating a service relationship for any service or task demian.app granst you or performs for you
Such services are entirely unrelated to your facebook account or data unless otherwise specified and in such situations an appropiate terms of service will be published and shared with you (along a more advanced facebook login option)