Fix creation of end date for rollover membership

[maneesha]

When we rollover a membership, we typically want the new membership to start the day after the source membership ends, and end a year after the new membership begins.

In the function to create the rollover membership, we successfully set the start date. However, because of the way the end date is calculated, we end up with an error in leap years. For example, a membership that started 2023-03-01 would end 2024-02-29. A rollover membership should start 2024-03-01 and end 2025-02-28. The current code tries to create the invalid date of 2025-02-29.

The recommended change is that the new end date should be the new start date plus one year, not the start year plus one.

[maneesha]

Marking this as medium priority because it is a bug and relatively easy to fix but also won't matter again until 2028.