Twins do not require duplicate identical class-year values

For GiveCampus school settings.

Allow Multiple lets a parent select distinct affiliation values, not count the same parent twice by saving the identical year twice. Parent/class participation is a donor calculation, not a count of children in the household. Define whether the leaderboard measures parent donors or student households; use the supported denominator or reviewed class adjustment for that policy rather than duplicating a gift or inventing a second parent identity. Parent aggregate adjustments do not automatically propagate to every tier layout.