Does quotes.Aggregate(PeriodSize.Week) use a fixed calendar week?

[DaveSkender]

The quotes.Aggregate(PeriodSize.Week) utility likely uses a rolling 7-day week instead of a fixed week with a specific day (e.g. Saturday) as the end -- which may be more preferred in most use cases.

• confirm its behavior with additional unit tests
• update documentation to clarify exactly how it boxes dates at each size
• consider providing overloads to allow both rolling or fixed calendar windows (e.g. with CalendarWeekRule)

Originally posted by @DaveSkender in #1183 (comment)

[DaveSkender]

The fix here is likely to make the non-TimeSpan variant of this method only use fixed calendar windows, like we do in our regular week block code for Pivot Points.

... switch {
  PeriodSize.Month => d.Month,
  PeriodSize.Week => EnglishCalendar.GetWeekOfYear(d, EnglishCalendarWeekRule, EnglishFirstDayOfWeek),
  ...

to do

• only use fixed calendar window, not the rolling 7-day period, for week
• update and clarify in documentation
• test that sub-week variants can be done this way as well. It may require more def on CalendarWeekRule as the arbitrary starting date e.g. for 3-day / 15-minute. Do we need one rule for each window size?