Add option to only track unique impressions and clicks (within a certain time-window)

Firstofall: We won't implement this, unless someone sponsors it, as it's quite a heavy addition. Feel free to contact us, if you'd like to have this implemented or provide a MR yourself.

Problem/Motivation

Currently, all impressions and clicks are tracked, while for many cases it makes sense to also keep track of only unique impressions (from the same IP within a given time window e.g.).

This could even be added as a further ad_tracker_unique submodule maybe or just get integrated into ad_tracker.
We need to take care of privacy topic, like for example by keeping the readable IPs etc. using best practices.

To be able to keep track of the unique clicks / impressions we'd nevertheless have to use a dedicated table with an entry per unique user.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes