create roles as normal user

Hello,

I want a "normal" user to create roles inside the database.
Is it only possible through the createrole privilige, or is there
something like sudo possibile.

I thought it is possible with the security definer option in create
function, but that does not work for me: (In this test the function was
created as superuser).

```sql
CREATE OR REPLACE FUNCTION add_db1_user() returns void language sql
STRICT security definer AS $$
CREATE ROLE db1_testuser login password 'secret';
$$

ERROR: permission denied to create role

Best regards
Johannes