Deal with postgresql privileges

[mathieubossaert]

COPY FROM program requires to be invoked by a superuser.
So we need to create Central2PG functions as a superuser and set security definers for functions using COPY FROM program
in order to be usable by an non superuser role.

[mathieubossaert]

https://www.cybertec-postgresql.com/en/abusing-security-definer-functions/