Check a sync window and return it in canonical form (dates trimmed). Throws
OpenKaValidationError for a since/until that is not a YYYY-MM-DD
calendar date, an until before since, a period outside PERIOD_RANGE and
a limit below SYNC_LIMIT_MIN (both integers), and refs that syncRefsProblem
refuses (trimmed otherwise). Idempotent; omitted fields stay
omitted. sync() calls it first.
Check a sync window and return it in canonical form (dates trimmed). Throws
OpenKaValidationErrorfor asince/untilthat is not aYYYY-MM-DDcalendar date, anuntilbeforesince, aperiodoutsidePERIOD_RANGEand alimitbelowSYNC_LIMIT_MIN(both integers), andrefsthatsyncRefsProblemrefuses (trimmed otherwise). Idempotent; omitted fields stay omitted.sync()calls it first.