Storing a total base_qty value in slab headers

[crocodiledundalk]

It may be useful for some use cases to store a value which tracks the total base_qty currently listed on a given slab.

While this could be tracked on the calling program side, I would suggest this is also an asset / use-case agnostic feature that might be useful for a number of cases.

An example case might be where a market order (or any order for that matter) should be capped so as not to take more than some % of the available volume. It may be generally useful to have an easily accessible metric/summary of volume available on the book.

Suggested approach would be to:

• Increment this value by base_qty base_quantity of the new Leaf_Node posted
• Decrement this value each time Out.base_size each time an Out is generated

[tomland123]

Personally just had this convo w/ Henry a bit back. This adds a lot of overhead to the orders account and while it does have huge UX benefits there is a pretty severe cost to adding so many bytes to the slab.

I am personally in favor of this change though.