Update simple_authentication, by Joschi (e-mail unknown)

"I have added two things.

1. modified snauth to work with courier userdb
   Setup a NewsServer Passowrd for a user:
    > userdbpw -hmac-md5 |userdb sample@somedomain.org set newspw

2. add the script (derived from https://github.com/liu-chong/sn/tree/master/contrib/simple_authentication)
   (see attachement)

3. modified SNPOST to verify the sender against a file in the newsgroup that says
   .allow
      sample@somedomain.org

Works perfectly for me... (Tested with Thunderbird...)

(only missing TLS/SSL...)"