[feature]: Enable sending of multiple different assets with one send transaction

[rkedez]

Is your feature request related to a problem? Please describe.

When sending assets, all Taproot Asset addresses must be of the same asset ID (see e.g. code comment in rpcserver.go). Therefore, sending many assets would necessitate making many BTC on-chain transactions with infeasibly high transaction costs.

Describe the solution you'd like

Ideally, I would like to send many different unique assets (e.g. 100k collectibles) with one send transaction and, respectively, one BTC on-chain transaction. When I asked about this feature on Slack some time ago, @guggero suggested that it involves anchoring multiple vPSBTs into a single transaction for which everything should be in place.

[ffranr]

tapd currently supports anchoring one vpsbt only, see:

taproot-assets/rpcserver.go

Line 1750 in 76bb5ae

return nil, fmt.Errorf("only one virtual PSBT supported")

I'll make an issue to enable multi vpsbt anchoring. I don't think an issue currently exists for that.