Implement concept of "tracks" for mobile boxes

[ubergesundheit]

From a discussion between @noerw @mpfeil and @ubergesundheit

Currently, the route /boxes/:boxId/locations returns all locations ever recorded for a box. The response is used for draw the locations of the box on the map.

Opening a graph of a sensor displays the last recorded 48 hours.

There is a visual connection between the locations on the map and the graph. (with colors, on mouseover, ...)

Several Problems:

• If there are many locations, displaying will be cluttered and slow
• Only the last recorded 48 hours will be colored?

We need a concept of "tracks" for mobile boxes to organize and unclutter measurements.

• Tracks are saved in the box as an array of timestamps (optional with a name)
• A route (for example /boxes/:boxId/tracks/start) starts a new track and saves the start timestamp in the tracks field of a box.
• Starting a new track ends the previous track (by saving a new timestamp in the tracks array)
• Measurements can then be queried through limiting the timestamp to a tracks start and the next tracks start timestamp

Later:

• Routes for track management
  • Renaming
  • Deleting

Anything I forgot @noerw @mpfeil ?

[noerw]

This feature should fall back gracefully when no track is ever created by the user. This would be useful for continuously running devices.
Options that come to mind:

1. (currently implemented) limit the shown trajectory to the same time interval as for measurements (currently 48h)
2. autodetect tracks by finding gaps of more than 30minutes in the location history
3. autodetect tracks based on some spatiotemporal filter (distance per hour?)

also: 💯

[mpfeil]

we should also include @robarto to this discussion