PostgreSQL: Create read-only database user/role

postgresql_create_ro_user.sql

CREATE USER username WITH PASSWORD 'the_password';
GRANT CONNECT ON DATABASE the_database TO username;
GRANT USAGE ON SCHEMA public TO username;
ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT ON TABLES TO username;
 
-- has to be executed while connected to the actual database
\c the_database
GRANT SELECT ON ALL SEQUENCES IN SCHEMA public TO the_database;
GRANT SELECT ON ALL TABLES IN SCHEMA public to the_database;