Add privacy zones

[opatut]

Users should be able to edit their privacy zones.

• Add a database model
• Add CRUD routes (REST)
• Implement a way to pass privacy zones to track processing (in openbikesensor/OpenBikeSensor-Scripts)
• Distinguish between public (with anonymization) and private (without) datasets, process each track twice
• Switch between public/private datasets based on context and visibility
• Build frontend to manage per-user privacy zones (basic functionality)

[opatut]

I've assigned myself because I have a WIP branch. I might push it later when we're done merging repos and then unassign myself, for somebody else can then continue to work on that branch. Hit me up if you're interested.

[amandel]

Not sure if you saw openbikesensor/OpenBikeSensorFirmware#216 - I would still stick with our current solution and close the linked issue - might be you have a different opinion?

[opatut]

Yes I saw it. I want to get started with circular regions first, and then expand it maybe later. I think it's a good idea, but I'd rather keep it simple for now. If we store the geometry as GeoJSON and use a GeoJSON library to evaluate the region in the filter, it'll be very easy to upgrade to other shapes (Polygons) in the future.

[amandel]

So we keep the current definition of the privacy areas. On the portal side there there might be the possibility to define different shapes in the future.