Support realtime periods in API v2

[RobertJoonas]

Changes

• Parse query date ranges into a new NaiveDateTimeRange struct rather than a simple Date.Range
• support realtime and 30m date range shortcuts in the private API JSON schema
• make it possible to pass a date parameter relative to which the date_range will be constructed.

Tests

• [x] Automated tests have been added

Changelog

• [x] This PR does not make a user-facing change

Documentation

• [x] This change does not need a documentation update

Dark mode

• [x] This PR does not change the UI