Validate and normalize a session list into the calendar's canonical form:
sorted by open, dates unique, each session well-formed (open < close,
breaks inside [open, close], sorted, non-overlapping). Throws on any
violation — a calendar must never be built from an inconsistent schedule.
Sessions must also be non-overlapping with each other (a later session's
open is >= the previous session's close).
Validate and normalize a session list into the calendar's canonical form: sorted by
open, dates unique, each session well-formed (open < close, breaks inside[open, close], sorted, non-overlapping). Throws on any violation — a calendar must never be built from an inconsistent schedule. Sessions must also be non-overlapping with each other (a later session'sopenis>=the previous session'sclose).