Configure SSH agent forwarding in Vagrant

When managing project dependencies with tools like composer then at some point you will inevitably have a dependency on private library sitting somewhere in private git repository. On production this is solved easily by adding deployment key. In case of developer’s virtual machine solution is not hard either: SSH agent forwarding. It can be configured in Vagrantfile in one line (next to configurations of provider and provisioner):

config.ssh.forward_agent = true