Access setting for users, problem

We are going to give all our shell users access to Postgres so that every user has their own database that they use as
muchas they like but so that they can't create new databases. Also these databases should be totaly private to the user
thatowns it (ok, the "postgres" should have access to them) so that nobbody else can
connect/select/insert/update/create/drop/etc.

How do I do it ?

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