Configure database password to be secret

[dhimmel]

Previously, we had an insecure public login because we were only allowing local connections. Now since @ben-heil will start rotating, I wanted him to have read-only access for https://github.com/greenelab/hetmech/issues/150.

[dhimmel]

For the postgres database, currently hosted on my Penn computer, I changed the password for the dj_hetmech admin user from not_secure to something secure.

I created a new read_only_user with:

# https://stackoverflow.com/a/762649/4651668
create user read_only_user with encrypted password 'placeholder_password';
GRANT CONNECT ON DATABASE dj_hetmech TO read_only_user;
GRANT USAGE ON SCHEMA public TO read_only_user;
GRANT SELECT ON ALL TABLES IN SCHEMA public TO read_only_user;

You can login with (if you know the password):

psql --dbname=dj_hetmech --host=phr-greene-007.med.upenn.edu --username=read_only_user --port=5432

Here are the current roles (via \du):

                                      List of roles
   Role name    |                         Attributes                         | Member of 
----------------+------------------------------------------------------------+-----------
 dj_hetmech     | Superuser, Create role, Create DB, Replication, Bypass RLS | {}
 read_only_user |                                                            | {}