New server::admin_password_hash parameter

[traylenator]

Pull Request (PR) description

Allow mongdb to be set up with the specification of a hash of the password rather than a password itself.

For example:

class{'mongodb::server':
  create_admin  => true,
  admin_username => 'admin',
  admin_password_hash => '5b1b54d081b35a00539780ab55e0ebf4',
}