create user with database and contrib

hello,

is there some simple way, how to do this???

I need to create user 'diplo' with no database create and no add users
privileges...

createuser -A -D -P -E -U root diplo

after that I create database 'diplo';

I need to import ltree into database 'diplo' with user diplo, but I
can't add grant access to language 'c', because only superusers can do
that...

thanks, miso