lncli: add missing wallet psbt sign sub command

[guggero]

Change Description

The walletrpc.SignPsbt didn't have a corresponding lncli command, which this PR now fixes.

Steps to Test

lncli newaddress p2wkh
{
    "address":  "bcrt1qkjha6h334gw5rxkcfecu2yldcrzetm0x0t7yqs"
}

lncli wallet psbt fund --outputs='{"bcrt1qkjha6h334gw5rxkcfecu2yldcrzetm0x0t7yqs":50000}' --sat_per_vbyte 2
{
    "psbt": "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",
    "change_output_index": 1,
    "locks": [
        {
            "id": "ede19a92ed321a4705f8a1cccc1d4f6182545d4bb4fae08bd5937831b7e38f98",
            "outpoint": "05d829f05d207120a105a083de850641ad86e4ec21960103fb5d8f93b283f440:1",
            "expiration": 1774337236,
            "pk_script": "ABRqqpL/eoL2UVDquWayDlstPJi11A==",
            "value": 500000000
        }
    ]
}

lncli wallet psbt sign cHNidP8BAHECAAAAAUD0g7KTj137AwGWIezkhq1BBoXeg6AFoSBxIF3wKdgFAQAAAAD/////AlDDAAAAAAAAFgAUtK/dXjGqHUGa2E5xxRPtwMWV7eaWoMwdAAAAABYAFFZYcLBeOebrcHh1NrGUlx8dKuoWAAAAAAABAN4CAAAAAAEBdUeQyYiHDnAmqRykNoawpyANg2CN+zHSOk+P2OoEpL8BAAAAAP3///8C3Jud0AAAAAAWABQDHAPbN+zpkNkpdtcP9LeRpY1bkwBlzR0AAAAAFgAUaqqS/3qC9lFQ6rlmsg5bLTyYtdQCRzBEAiAQLleYosHT
TQFT8GmV6pVwmffxNMm6zSrgc4Ug8W1hpQIgNIqJ3Nw7scyOyjBDXKUnGpD49Thjd1pxFYHJ5fDcOYABIQPL08RdZUkJuQNZx7kZBKCWcJNgwsFxsW1auNWJxiGvWHcAAAABAR8AZc0dAAAAABYAFGqqkv96gvZRUOq5ZrIOWy08mLXUAQMEAQAAACIGAyrOdtfVuHfFNtox6HaUwAH+fCubYl+XjEFBt3SYzyXvGAAAAABUAACAAAAAgAAAAIAAAAAAAAAAAAAAIgIDfRZgefLy9FzYiu2Eym18AqjBhYXQgBKJ+Zs5Elu5k8YYAAAAAFQAAIAAAACAAAAAgAEAAAAAAAAAAA==
{
    "psbt": "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",
    "signed_input_indexes": [
        0
    ]
}

Pull Request Checklist

Testing

• Your PR passes all CI checks.
• Tests covering the positive and negative (error paths) are included.
• Bug fixes contain tests triggering the bug to prevent regressions.

Code Style and Documentation

• The change is not insubstantial. Typo fixes are not accepted to fight bot spam.
• The change obeys the Code Documentation and Commenting guidelines, and lines wrap at 80.
• Commits follow the Ideal Git Commit Structure.
• Any new logging statements use an appropriate subsystem and logging level.
• Any new lncli commands have appropriate tags in the comments for the rpc in the proto file.
• There is a change description in the release notes, or [skip ci] in the commit message for small changes.

📝 Please see our Contribution Guidelines for further guidance.

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a new lncli command, wallet psbt sign, to expose the existing walletrpc.SignPsbt functionality to users. This enhancement provides more granular control over Partially Signed Bitcoin Transactions (PSBTs) by enabling users to sign inputs belonging to their wallet without immediately finalizing or publishing the transaction. It significantly improves lncli's wallet management capabilities, offering a crucial step in multi-party or complex transaction workflows.

Highlights

• New lncli command: A new lncli wallet psbt sign command has been added, allowing users to sign Partially Signed Bitcoin Transactions (PSBTs) directly from the command line.
• Updated finalizePsbt description: The description for the lncli wallet psbt finalize command has been updated to clarify its specific use cases and to reference the new sign subcommand for broader signing needs.

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[gemini-code-assist]

Code Review

This pull request adds the lncli wallet psbt sign command, which was missing for the walletrpc.SignPsbt RPC. The changes look good overall. I've added a couple of suggestions to improve documentation and adhere to the coding style guide.

[gemini-code-assist]

According to the repository style guide (lines 17, 18), every function must have a comment that starts with the function name. The signPsbt function is missing this documentation.

Suggested change

	func signPsbt(ctx *cli.Context) error {
	// signPsbt handles the `lncli wallet psbt sign` command.
	func signPsbt(ctx *cli.Context) error {

References

1. Every function must be commented with its purpose and assumptions. ^(link)
2. Function comments must begin with the function name. ^(link)

[bhandras]

LGTM, thanks Oli!

[ellemouton]

noice 🙏 just needs linter fix

[guggero]

noice 🙏 just needs linter fix

Oops, I must be out of practice, don't know how I could've let a too-long line slip past 😬