ServerUser.enabled method to return enabled users
Implement Server.switch_user

Add User.switched_from attribute
Add User.switched_to? method
Add Server.switch_user
Add Server.exec_with_context as wrapper to prepend "sudo -u <username> bash -c " to Server.exec
Update login_params to utilize current_user or current_user.switched_from if current_user.switched_to? is true