Possibility to add credentials to the curl PURGE request

[rorentz]

First of all, great extension and idea! i really like it.

It would be greate to provide the possibility to set credentials for the curl request to have your extension working on dev systems where basic_auth is activated. May be just a signal/hook like here : https://github.com/lochmueller/staticfilecache/blob/2913e0abcc054ae33177868fe49a3e6820e1bbb2/Classes/Service/ClientService.php Line 87

Greetings!