Reference apex_workspace_apex_users or wwv_flow_fnd_user in a foreign key constraint

What I'm trying to do is to extend authorisation upon APEX basic users to use it as conditions of pages rendering. I would like to create additional tables to store some workspace specific info about users. Is it possible to reference wwv_flow_fnd_user.user_name or apex_workspace_apex_users.user_name as a foreign key constraint? If yes, how to? If no, what's the alternative to bind APEX user info with my own additional info on database level? I've tried: - CONSTRAINT FK_USER_NAME FOREIGN KEY (USER_NAME) REFERENCES apex_workspace_apex_users (USER_NAME) ON DELETE CASCADE - CONSTRAINT FK_USER_NAME FOREIGN KEY (USER_NAME) REFERENCES wwv_flow_fnd_user (USER_NAME) ON DELETE CASCADE - CONSTRAINT FK_USER_NAME FOREIGN KEY (USER_NAME) REFERENCES APEX_190100.wwv_flow_fnd_user (USER_NAME) ON DELETE CASCADE All of this both as SYSDBA and as an owning schema of an APEX workspace. All I've got so far is a bunch of errors like insufficient priviliges and table or view does not exist.