Hi Maxim,

I guess this is not explained that well, but the service-extension
snippet is supposed to go under the (extensions ...) field of a
<service-type> record.  If you want to extend this in your system
config, you want (simple-service ...) instead, with e.g.

--8<---------------cut here---------------start------------->8---
(simple-service 'alice-role postgresql-role-service-type
                (postgresql-role
                 (name "alice")
                 (create-database? #t)))
--8<---------------cut here---------------end--------------->8---

Best,
-- 
Josselin Poiret