Implement done feature

[mhewedy]

Users should send done command after paying for the invoice.

Lunchy keeps sending notifications every couple of hours for users who were involved in lunch activity but didn't pay for the lunch yet (didn't send the done command)

the scope for this should be 1 day only, everything should reset with the new day

The notification can be sent directly to the user, instead of to be sent to everyone in the group.

technical guidance

• we will implement 1 command and 1 job here
• we will have a list of done (done_list) that we will add to if the user sends the done command
• every couple of hours, we will run the job to compare this list with the list of the users involved in the lunch activity
• The done_list should reset with the new day (when the heads-up message is sent to remind users)
• the notification should be sent during convenience hours, e.g. from 4 pm to 10 pm, and from 9 am to 11 am, and shouldn't be sent at night,
• The notification can be sent directly to the user, instead of to be sent to everyone in the group.