Facebook social login base url, authorize url, token access url? updated step by step

hi there fellows,

i’d like to demosntrate to a prospect the social login with facebook.
but i’m in pain to make it work.
the issue are the other urls.
i was able to put social login to work with other applications, and it was never an issue.
however, in erpnext some additional urls are needed, and i don’t know how to fulfill them
so far it does not appear the facebook button in the login screen.

i’d appreciate any help.

best regards,

fernando a. bender