robertdebock.users: Add ansible.posix.authorized_key exclusive option

[jkirk]

Describe the change

Added a new option user.exclusive_keys which allows to set the exclusive parameter of the ansible module ansible.posix.authorized_key :

Quoting ansible.posix.authorized_key module:

exclusive (boolean):

  Whether to remove all other non-specified keys from the authorized_keys
  file.

  Multiple keys can be specified in a single key string value by
  separating them by newlines.

  This option is not loop aware, so if you use with_ , it will be
  exclusive per iteration of the loop.

  If you want multiple keys in the file you need to pass them all to key
  in a single batch as mentioned above.

  Choices:

  * false (default)
  * true

This parameter has been tested locally in our environment.

Closes: #42