Supervisor Notification Filtered By Requestor Balance

[carolyncole]

As a supervisor, I want requests only if the balance supports it so that I don’t make an impossible approval.

related to #16

I wonder if we will allow requests by requestors if they do not have available balance. This will get into calculating future balance. Aka Request is being generated in January for July, so the user does not have enough balance now, but will have the balance in July.

[hackartisan]

This may be in conflict with feedback we heard that there may be use cases for allowing negative balance. Also this use case is partially addressed by #169