Karrot to connect to postgres via unix domain socket

On the server I added a couple of lines into `/etc/postgresql/13/main/pg_hba.conf`

```
local fstool-dev fstool-dev md5
local karrot-world fstool md5
```

And then in `.env` (or `karrot.env` in here...) just adding:

```
DATABASE_HOST=
```

(as blank means try unix domain socket see https://docs.djangoproject.com/en/4.2/ref/settings/#host)
