Class Throttler implements the bruteforce protection for security actions in
Nextcloud.
It is working by logging invalid login attempts to the database and slowing
down all login attempts from the same subnet. The max delay is 30 seconds and
the starting delay are 200 milliseconds. (after the first failed login)
* add uri to AddressBookImpl array
* Introduce ImageExportPlugin for CardDav
* add plugin to v1 routes
* replace binary contact photo with link
* update tests
* Adding unit tests
