Required for dual funding where the opener sets it.
Changelog-Added: JSON-RPC: `fundpsbt` takes a new `locktime` parameter
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
It's *possible* to do this using various RPC calls, but it's
unfriendly:
1. Call getinfo to get the current block height.
2. Call listfunds to map the UTXOs.
3. Create the PSBT and hope you get all the fields correct.
Instead, this presents an interface just like `fundpsbt`, with identical
returns.
I think it's different enough to justify a new command (though it
shares much internally, of course).
In particular, it's now quite simple to create a command which uses
specified utxos, and then adds more to meet any shortfall.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
fundpsbt forces the caller to manually add their weight * feerate
to the satoshis they ask for. That means no named feerates.
Instead, create a startweight parameter and do the calc for them
internally, and return the feerate we used (and, while we're at it,
the estimated final weight).
This API change is best done now, as it would otherwise have to
be appended as a parameter.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
