auth-gen-token: Add --auth-gen-token option

auth-gen-token: Add --auth-gen-token option

This sets the flag if the OpenVPN server should create authentication
tokens on-the-fly on successful --auth-user-pass-verify or --plugin with
OPENVPN_PLUGIN_AUTH_USER_PASS_VERIFY processing.

If an OpenVPN server is running without this option, it should behave
as before.  Next patches will implement the auth-token generation and
passing it on to the clients.

The --auth-gen-token can be given an optional integer argument which
defines the lifetime of generated tokens.  The lifetime argument
must be given in number of seconds.

  v2 - Update Changes.rst
     - Improve man page in regards to lifetime argument
     - Rename struct member auth_generate_token to auth_token_generate
       to have a consistent naming scheme

Signed-off-by: David Sommerseth <davids@openvpn.net>
Acked-by: Steffan Karger <steffan@karger.me>
Message-Id: <1477684124-26083-2-git-send-email-davids@openvpn.net>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg12825.html