Changes

Approximate points marking:

• New field for data point (Point in proto) indicating whether the data is approximate (whether it should be drawn as such). Currently all those marks are placed on trailing subsequent points.
• The field is omitted for false values in json serialization for efficiency. Absence of the field should be treated as false (meaning the data is not approximate == exact)

Noticeable changes in stats service:

• Regardless of requested interval, no future points are now returned.
  • Previously they were generated according to settings; e.g. if one were to request data for 10 days forward.
• Improved handling of near-today dates.
  • Previously was mitigated by manual removal of last point. It prevented new updated values from being shown until the end of the day. Now they will be returned as soon as they become available.
• Added limit for maximum requested interval; it was possible to request server to generate data points for all days for ~ 10 000 years, which might be vulnerable to DoS (easy to fix so added just in case). The limit is configurable, default value - 500 years (max request processing time change from ~200ms to ~50ms).

Other:

• Development docker compose for stats service
• Restructure in stats service source code to accomodate the changes
• Readability improvements
• Updated timestamp columns in stats db to consider timezone. Did not cause troubles yet; a preventive measure.
• Pass time as argument instead of calling ..::now() during update (for better testability)