How to securely isolate databases/users in a multi-tenant Postgresql?

I want to make a service that gives each of my users their own PG user and
database. I want to keep them isolated from each other. There are no
special extensions installed, it's a pretty vanilla PG cluster.

Are there any considerations beyond making each person their own user and
owner of their own database like this, and letting them connect to the
database?

```
create user u2745;
create database d2745 owner u2745;
-- etc.
```