Add the ability to deploy Postgres in containers

[ruslanloman]

Hello,

Thank you for your great project.

Have you considered the option to deploy Postgres/Patroni/etcd/Haproxy in containers instead of installing packages. This approach has many advantages.

1. Easier cluster upgrades without worrying about package dependencies.
2. Provides an OS-agnostic setup.
3. Use docker upstream images for postgres, etcd.

Thank you!