Set magic ENV varialbes for user, default DB

instead of doing it ourselves

docker/Dockerfile.postgres

@@ -1,6 +1,5 @@
 FROM postgres:10
 
-ENV POSTGRES_USER postgres
 # Do not require a PostgreSQL superuser password.
 # See https://github.com/docker-library/postgres/issues/681.
 ENV POSTGRES_HOST_AUTH_METHOD trust

docker/entrypoint.postgres.sh

@@ -10,8 +10,6 @@ if [ ! -f /var/lib/postgresql/data/setupFinished ]; then
         sleep 5
     done
     >&2 echo "### importing table schemas"
-    su postgres -c 'createdb invidious'
-    su postgres -c 'psql -c "CREATE USER kemal WITH PASSWORD '"'kemal'"'"'
     su postgres -c 'psql invidious kemal < config/sql/channels.sql'
     su postgres -c 'psql invidious kemal < config/sql/videos.sql'
     su postgres -c 'psql invidious kemal < config/sql/channel_videos.sql'