YaCy Search Authorization and Authentication

WHAT IS THIS?
The purpose of this service is the authentication of search users;
it does an authentication of users and identifies their user rights.
Such rights are expressed with sets of specific collections names
which had been used to index data in the YaCy search engine.
This is done using a reverse proxy to a YaCy search server. It
serves as a filter for search requests from a JSON search
client like https://github.com/yacy/yacy_webclient_bootstrap
The server attribute within the searchpage_template_yaml4 must point
to the location of this file on a php-enabled server.

WORKFLOW
The authorization is done in an external system (i.e. LDAP server
like Active Directory). The external system names access domains
for the user which is matched with collection names in this module.

HOW TO INSTALL
- copy this file on a web space with a php interpreter
- modify the php.ini file and set the attribute allow_url_fopen to 1
- change the external_url path in this file and let it point to your
  own server
- modify the server address in searchpage_template_yaml4 and point
  it to the location of this file
- modify class/config.class.php, if necessary (default/guest collection
  name(s), type of user authentication, mapping of ldap/ad group names
  to yacy collection names

LICENSE
This is licensed under the Apache License Version 2.0, please see
file license.txt