(API) Break down pending revenue into timestamped blocks

[IMB11]

First part of simplifying the "pending" information on the dashboard. Will need this on staging or prod to develop the UI, having issues running it locally.

TLDR, updates the balance endpoint with a new pending_interval field which is an array of the following type:

pub struct PendingInterval {
    pub value: Decimal,
    pub date: chrono::NaiveDate,
}

It stores the value of money that will be moved into the balance when the NET 60 period is over (the end date specified by date)

Example:

{
	"balance": 192.481018470000000,
	"pending": 783.392947002803900,
	"pending_interval": [
		{ "value": 392.399202998400, "date": "1st March ... blah" },
		...
	]
}

[IMB11]

Replaced by #3283