addCalendarToList adds an existing accessible calendar to the connected
user’s Calendar list and can set initial display preferences.
Example
Inputs
calendar is the accessible calendar ID and is required even if the calendar
is not already in the user’s list. Optional backgroundColor and
foregroundColor require #RRGGBB; hidden, selected, and summaryOverride
set user preferences. notifications is an array of { type } where type is
eventCreation, eventChange, eventCancellation, eventResponse, or
agenda. account selects the Google account.
Output
Returns the new calendar-listCalendar; see Get calendar-list entry. The action subscribes to an existing calendar; it does not create or share one.