Add functionality to redact/filter sensitive data

[ErikBjare]

We need a model to filter out sensitive data by default.

For example if a window title contains: "[title] - Firefox (Private Browsing)" we should redact [title] to some magic string such as "REDACTED".

For some cases we might want to filter the window out entirely, giving 0 information about which window is running, better catch too much than too little.

It should be the goal that every user has a set of "clean" data. The filtering should also be able to be run on an existing database of data, so that cleaner data can be output. Preferably, the data should be so clean that there is little (or even no) reason not to share it (which would be great since easy access to a large dataset could make research in some areas a lot easier!).

The question left is where this processing step should take place. We want the filtering/redacting to happen before data is sent anywhere but it should also be able to be enforceable on a server (if the server owner doesn't trust the servers security, if in the cloud for example) and have clients notified of this so that they can do the filtering on their side, removing the need to send sensitive data at all. It might therefore be prudent to write a module in aw-core that implements this functionality since it should be useable from the server and all clients (which transmit sensitive data).

This feature should be on by default, we don't need anything advanced yet, first priority is to redact titles from Incognito/Private Browsing, that's a good step in the right direction.

This should have a far higher priority than Zero-Knowledge storage right now, because it's a lot easier and is more user friendly (In ZK storage: if you lose your keys you lose your data).

[ErikBjare]

Moved to ActivityWatch/activitywatch#1