[Spending Limit] Add warning email when balance is getting low

[garyhtou]

Send an email to the user when their spending limit is getting low. Something along the lines of:

hi, your Hack Club HQ spending controls balance is getting low. Your current balance is $23.

To top up your balance, please ask your manager to create an allowance here (link to their spending control page).

I'm not exactly sure what the threshold should be.

[sampoder]

10% of maximum balance?

[garyhtou]

"max balance" as in calculate the running balance and then get the maximum of those values?

yeah, that can work. I'd suggest

historic_max_balance_cents = # as described above
threshold = [historic_max_balance_cents, 25_00].max

[sampoder]

"max balance" as in calculate the running balance and then get the maximum of those values?

yep

[garyhtou]

Cool!!

historic_max_balance_cents = # as described above
threshold = [historic_max_balance_cents, 25_00].max

Let's go with this!