Support private routing hints

[seth586]

Right now, inbound liquidity on a private channel will not work unless a private routing hint is added.

[sommerfelddev]

According the lnd rest api docs for AddInvoice it seems to be as easy as adding private=true in the rest api request.

According to my shallow investigation, it should be added in these places:

ligess/router.js

Lines 47 to 53 in d8c7162

	const invoice = await unaWrapper.createInvoice({
	amountMsats: msat,
	descriptionHash: crypto
	.createHash('sha256')
	.update(metadata)
	.digest('hex')
	})

https://github.com/blc-org/una/blob/c4ae26440081b29f8a0f3b950a1be948dc9cb872/bindings/una-js/index.d.ts#L22-L32

Maybe this should be behind an environment variable like LIGESS_LND_PRIVATE_INVOICES. @Dolu89 what do you think?

[Dolu89]

Ligess currently uses the original node.js of Una (master branch). This https://github.com/blc-org/una/blob/c4ae26440081b29f8a0f3b950a1be948dc9cb872/bindings/una-js/index.d.ts#L22-L32 is part of the new version of Una written in Rust. It's not finished, so not deployed yet.

The current node.js version of Una wasn't supposed to be updated, but I'll see how to add this later