Feature: Fixed payments reminder

[FolkLoreee]

Background

To help the house treasurer with consolidating house-related expenses, the bot should be able to:

• automatically send reminders
• keep track of which house members have yet to pay
• consolidate receipts for claims

AC

As a house member, I should be able to...

• receive a reminder to pay X amount to House Treasurer every month Payment reminder: Generate automatic reminder 1 day before payment is due #10
• read and update the payment status by using /pay command. Detailed workflow will be described under the subtask ticket Payment reminder: Read, Update each payment status #11.