use project name for postgres user

[yuchunc]

Current setup, postgres user will default to postgres. This PR will use project name instead.

[reachfh]

We still need the postgres admin user postgresql_admin_user. That's the "root" user for posgres, and it's useful for this user to be able to connect to the database without a password for admin scripts and when things are messed up.

The app should generally talk to the database with a password. It's not safe to give the app user admin permissions without a password. It might make sense to add a line which gives passwordless access to a specific database.

[yuchunc]

Gotcha, that make sense.

I have updated db-servers/postgres.yml, can you take a look again?
Thanks!

[reachfh]

I think it's unnecessary, though. By default you can connect to any local database with a password by connecting to 127.0.0.1 using this line:

- { type: host,  database: all, user: all, address: "127.0.0.1/32", method: "{{ postgresql_default_auth_method }}", comment: "IPv4 local connections:" }

The Elixir Postgres db driver uses TCP. I don't think it supports Unix domain sockets.