List the official full names of all the legislators who have facebook, instagram, twitter and youtube accounts.
have facebook, instagram, twitter and youtube accounts refers to 'facebook' is not null AND 'instagram' is not null AND 'twitter' is not null AND 'youtube' is not null;
SELECT T1.official_full_name FROM current AS T1 INNER JOIN `social-media` AS T2 ON T1.bioguide_id = T2.bioguide WHERE T2.facebook IS NOT NULL AND T2.instagram IS NOT NULL AND T2.twitter IS NOT NULL AND T2.youtube IS NOT NULL