Moodle Custom User Profile Fields
These fields allow users to enter in their relevant ids for the social networks shown above. At the moment nothing is done with this data except shown on their Moodle profile page, but the long term plan is to enable social icons throughout Moodle with links to the relevant social networks.
Taking this a step further, I will even look into using available API's to directly integrate content into Moodle to help with user engagement.
In the mean time, if you would like to add Custom User Profile Fields for your Moodle, you can do so in the Administration menu.