FTX: Margin lending/borrow rate history (#981)

* Adds lending rates/borrows to FTX and the command

* Movements, renames, rpc test

* Fleshing out rpc response

* Allows rpcserver to calculate offline (but not gctcli). Expands tests

* rn structs. add exchange_wrapper_issues support

* Adds a nice yearly rate

* Surprise yearly borrow rate!

* Rn+Mv to margin package. Fixes some serious whoopsies

* Adds average lend/borrow rates instead of sum

* rm oopsie whoopsie

* This is what the linter was having an issue with

* re-gen

* lintl

* niteroos

exchanges/order/order_types.go

@@ -23,7 +23,10 @@ var (
 	ErrAmountIsInvalid            = errors.New("order amount is equal or less than zero")
 	ErrPriceMustBeSetIfLimitOrder = errors.New("order price must be set if limit order type is desired")
 	ErrOrderIDNotSet              = errors.New("order id or client order id is not set")
-	errCannotLiquidate            = errors.New("cannot liquidate position")
+	// ErrNoRates is returned when no margin rates are returned when they are expected
+	ErrNoRates = errors.New("no rates")
+
+	errCannotLiquidate = errors.New("cannot liquidate position")
 )
 
 // Submit contains all properties of an order that may be required