membership start date #57
Description
determine if harvest is active based on when a plot "joined" the cooperative.
in other words, can have someone with farms dating back to the 90's but joined in 2002, don't want their yields showing up as part of the total unless we explicitly toggle them to.
is_active considers time as in age of the plot, but we can encode 'join_date' as a feature, and if present, make sure that exceeds the present time.