To finish the install of mod_auth_pgsql, you need
to enable the module using the following command

  ${PREFIX}/sbin/${MODAPACHE_ENABLE}

You should also read
  ${PREFIX}/share/doc/mod_auth_pgsql/mod_auth_pgsql.html

If you already have Apache running on your machine,
you should not use "apachectl restart" - instead,
you should fully stop and then restart the server.