staticaddr: psbt withdrawals

[hieblmi]

This PR a new rpc for withdrawals via psbts,

rpc ServerPsbtWithdrawDeposits (ServerPsbtWithdrawRequest)
        returns (ServerPsbtWithdrawResponse);

[gemini-code-assist]

Summary of Changes

Hello @hieblmi, 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 enhances the static address withdrawal mechanism by integrating Partially Signed Bitcoin Transactions (PSBTs). It introduces a new RPC for PSBT-based withdrawals and refactors several core utility functions into a dedicated package, streamlining the process of cooperative transaction signing and improving modularity within the codebase.

Highlights

• New RPC for PSBT Withdrawals: A new RPC endpoint, ServerPsbtWithdrawDeposits, has been introduced to facilitate withdrawals using Partially Signed Bitcoin Transactions (PSBTs). This allows the client to construct the withdrawal transaction and the server to provide its signature.
• Code Refactoring to staticutil Package: Common utility functions related to Musig2 session creation, toPrevOuts conversion, and withdrawal transaction value calculations have been refactored into a new staticaddr/staticutil package. This improves code organization and reusability across the static address components.
• PSBT Integration in Withdrawal Process: The withdrawal transaction creation and signing flow has been updated to leverage PSBTs. The client now sends an unsigned PSBT to the server, which then signs it and returns the necessary signing information, allowing for a more flexible and standardized multi-party signing process.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description
Code Review	/gemini review	Performs a code review for the current pull request in its current state.
Pull Request Summary	/gemini summary	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in pull request comments and review comments.
Help	/gemini help	Displays a list of available commands.

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for Github and other Google products, sign up here.

You can also get AI-powered code generation, chat, as well as code reviews directly in the IDE at no cost with the Gemini Code Assist IDE Extension.

Footnotes

1. Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution. ↩

[gemini-code-assist]

Code Review

This pull request introduces a new RPC endpoint for PSBT-based withdrawals, ServerPsbtWithdrawDeposits, which enhances the flexibility and security of the withdrawal process by allowing the client to construct the transaction and the server to provide only the necessary signatures. The changes involve significant refactoring, moving common utility functions to a new staticutil package, and updating the withdrawal manager to use the new PSBT flow. The introduction of staticutil improves code organization and reusability. Overall, the changes are well-structured and align with best practices for handling Bitcoin transactions.