Chained container proxies can't work

[cbosdo]

All container proxies configurations have the server public SSH key to use as authorized key. This is fine for the first proxy in a chain but not the others.

Here is the setup that is expected:

• Proxy 0:

  • Proxy 0 SSH key pair
  • Server public key

• Proxy 1:

  • Proxy 1 SSH key pair
  • Proxy 0 public key

Each proxy should expose his own public key in apache's /pub directory to let the next proxy use it or this key needs to be copied in the ssh.yaml's server_ssh_push_pub field of the next proxy.

This also raises the question of rotation of those keys: we probably want to provide some helper tool for it.