Augment the time chopping job to compute convex hulls for session_segments

[ZavenArra]

In the time chopping job, we separate a session into session_segments. Once #103 is working correctly, we must extend this job to also compute convex hulls for each created session segment.

When a session is done processing, and all attached session_segments, have been created, each session_segment must have a convex hull geometry computed and updated into the convex_hull field.

A convex hull is generated by using the ST_Collect function postgis (part of the postgres data). https://postgis.net/docs/manual-3.0/ST_ConvexHull.html#:~:text=To%20compute%20the%20convex%20hull,shrink%2Dwrapping%22%20the%20geometries.

The job must call ST_Collect on all raw_captures in each session_segment. The resulting geometry is stored in the convex_hull field before the session.processed_at timestamp is update to now().