auth_mkhomedir - Autocreate a new account's home directory

       A callback_func that's passed as a parameter to auth_getuserinfo_meta(3)[1] can invoke this function to
       automatically create a new account's home directory, if the authlib client is running as root, forwarding
       the authinfo pointer from the callback.

       auth_mkhomedir() checks if the AUTH_MKHOMEDIR_SKEL environment variable is set, and if the authenticated
       account's home directory does not exist. If the environment variable is set it must point to a directory
       like /etc/skel that contains a template for the contents of a new account's home directory.

       If AUTH_MKHOMEDIR_SKEL is not set, or if the home directory exists, auth_mkhomedir() does nothing and
       returns 0. Otherwise the account's home directory gets created, and the contents of the
       AUTH_MKHOMEDIR_SKEL directory get recursively copied into the new home directory. The permissions of
       AUTH_MKHOMEDIR_SKEL and its contents are preserved, and the owner userid and groupid is set to the
       authenticated account's userid and groupid.

       auth_mkhomedir - Autocreate a new account's home directory

        1. auth_getuserinfo_meta(3)
           http://www.courier-mta.org/authlib/auth_getuserinfo.html

        2. authlib(3)
           http://www.courier-mta.org/authlib/authlib.html

Double Precision, Inc.                             10/28/2020                                  AUTH_MKHOMEDIR(3)

auth_mkhomedir() returns a non-zero value if an error occured while creating the new account's home
       directory.  auth_mkhomedir() returns zero if the new account's home directory was created successfully,
       or if the account's home directory already exists.

authlib(3)[2], auth_getuserinfo_meta(3)[1].

       #include <courierauth.h>

       intrc=auth_mkhomedir(structauthinfo*auth);