rpc: add asset hodl invoice support

[Roasbeef]

In this commit, we add hodl invoice support when creating invoice for TAP channels. The invoice creation proceeds as normal, but a special HodlInvoice field is set which contains a payment hash which must be set.

When invoices are created using this endpoint. They MUST be settled using the SettleInvoice RPC on the invoicesrpc server in lnd.

[coveralls]

Pull Request Test Coverage Report for Build 11789368763

Details

• 0 of 51 (0.0%) changed or added relevant lines in 1 file are covered.
• 27 unchanged lines in 7 files lost coverage.
• Overall coverage decreased (-0.05%) to 40.613%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
rpcserver.go	0	51	0.0%

Files with Coverage Reduction	New Missed Lines	%
tappsbt/create.go	2	53.22%
tapdb/multiverse.go	2	60.95%
internal/test/helpers.go	2	86.85%
commitment/tap.go	2	84.43%
asset/asset.go	2	80.02%
tapgarden/caretaker.go	8	68.5%
universe/interface.go	9	47.09%

Totals
Change from base Build 11782733093:	-0.05%
Covered Lines:	24684
Relevant Lines:	60779

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💛 - Coveralls

[guggero]

Linter isn't happy about line length and one question about a flag, otherwise LGTM 🎉

[GeorgeTsagk]

Lgtm

[ZZiigguurraatt]

why call it hodl invoice whereas everywhere in LND documentation hold invoice is used?

[ZZiigguurraatt]

Why do you have a separate HodlInvoice (https://lightning.engineering/api-docs/api/taproot-assets/taproot-asset-channels/add-invoice#tapchannelrpchodlinvoice) object with just a payment_hash in it? Do you expect to add more fields? LND's AddHoldInvoice (https://lightning.engineering/api-docs/api/lnd/invoices/add-hold-invoice) does not have this.

Also, AddHoldInvoice in LND uses hash instead of payment_hash. For new users, it is confusing if there is a difference. I think they should have common names everywhere. I think payment_hash is better to use than just hash.

[ZZiigguurraatt]

Also, at https://lightning.engineering/api-docs/api/taproot-assets/taproot-asset-channels/add-invoice/index.html#tapchannelrpcaddinvoicerequest it says to use an invoice_request generated from an Invoice (https://lightning.engineering/api-docs/api/lnd/lightning/add-invoice/index.html#lnrpcinvoice). Do we use this one for a HOLD invoice too, or an AddHoldInvoiceRequest (https://lightning.engineering/api-docs/api/lnd/invoices/add-hold-invoice#invoicesrpcaddholdinvoicerequest)? Note: AddHoldInvoiceRequest has the hash field, so that would be defined twice if it were to be used.