Clojure wrapper for the Google Calendar API (v3).

Provides idiomatic Clojure functions for managing events, calendars,
calendar list entries, access control, free/busy queries, colors,
and settings in Google Calendar.

Auth: use csl/scoped-delegated-credentials or csl/user-credentials with
the appropriate scope:
- CalendarScopes/CALENDAR              (full read/write)
- CalendarScopes/CALENDAR_READONLY     (read-only)
- CalendarScopes/CALENDAR_EVENTS       (events read/write)
- CalendarScopes/CALENDAR_EVENTS_READONLY (events read-only)
- CalendarScopes/CALENDAR_SETTINGS_READONLY (settings read-only)

All list functions return {:data [...] :next-page-token "..."}.
:next-page-token is absent when there are no further pages.

Update semantics: functions named update-* use PATCH (partial update);
functions named replace-* use PUT (full replacement). Both return
the updated resource.

All functions return {:data ...} on success or {:error ...} on failure.