monero-wallet-rpc: Add sub-address parameters to make_integrated_address API

[mmorrell]

Currently, the "make_integrated_address" API in monero-wallet-rpc only generates an integrated address for the main account (at address_index 0).

There should be a version of "make_integrated_address" which can work on sub-addresses. Such as make_integrated_address(address_index) and/or make_integrated_address(address).

This could be done adding by optional parameters to the existing make_integrated_address API.

e.g.

{
	"jsonrpc":"2.0","id":"0",
	"method":"make_integrated_address",
	"params": {
		"address_index": 3
	}
}

Use case: User wants to track individual payments to each subaddress.

[moneroexamples]

You mean making integrated sub-addresses? If so, this has been discussed already and the idea of integrated sub-addresses has been dropped.

#2056 (comment)

[krtschmr]

subadresses don't have payment IDs, or am i wrong?

[moneromooo-monero]

Subaddresses are supposed to obsolete payment ids.

[mmorrell]

Fair enough. Thanks for looking into this.