Please add "current borrowed amount" and / or "user equity"

**Is your feature request related to a problem? Please describe.**
I want to limit my algos to only trade 1x my cash amount, but the cash amount is delayed, and there's not really a great way to tell how much cash-secured equity I have... the "equity" includes money that actually belongs to Alpaca, I guess, since it's borrowed stock.

**Describe the solution you'd like**
I'd like a way to quickly get the amount of equity which is actually mine, as opposed to a lump sum which includes borrowed stock

**Describe alternatives you've considered**
Tradier, TDAM, Binance, Interactive Brokers

**Additional context**
My granddad told me never to invest with borrowed money. I am not going to invest money I borrow from Alpaca. It's that simple. If I can't compute the amount of *my* money I have in Alpaca at a point in time (not including the debt), then I must look elsewhere, because there's no way for me to safely use this API.

I do not think a brokerage API is useful if a user cannot easily figure out how much of their money they have in their account. It's also probably against the law, or would expose Alpaca to breach of contract lawsuit for breaching their account agreement. My account page shows I more than doubled my "equity" in a day, now I'd like to withdraw that "equity" -- where's my $200,000?