Implement digest feature

I checked that correct notifications are sent to users. So it works correctly.

@Łukasz Lewczyński You're right, it looks like it.

@Joanna Szymańska I think that those notifications are from the fulfillment service.

@Łukasz LewczyńskiI checked it again and as a chaz and the administrator only receives a notification about the new order, which is the one that comes after a minute. But instead of "There are $(count)requisitions have been converted to orders(...)" I get information every time that "Create an order: 6dc3cb6f-1f53-4681-b27e-3f835261ffcb with status: TRANSFER_FAILED":

@Łukasz Lewczyński I have tested this ticket and no notifications related to requisition are coming to the user, both those that should be after a minute and those that should be after 5 minutes.