docs: added a user guide for db migration

[saubyk]

Change Description

Added a user guide for database migration journey on LND.
This guide would be updated as LND data stores are incrementally migrated to relational database.

[gemini-code-assist]

Summary of Changes

Hello @saubyk, 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 user guide for LND node operators, outlining a strategic two-stage database migration process. The guide facilitates the transition from the existing bbolt key-value store to more scalable and performant SQLite or PostgreSQL backends. It details how to first migrate to a SQL-based key-value database and then incrementally move specific LND subsystems to a fully relational database structure, aiming to resolve performance bottlenecks and enhance operational efficiency.

Highlights

• LND Database Migration Guide: Introduces a new comprehensive user guide for LND node operators, detailing a two-stage process to migrate from the legacy bbolt key-value store to modern SQLite or PostgreSQL backends.
• Two-Stage Migration Process: Explains the migration in two stages: first, from bbolt to a SQL-based kvdb using the lndinit tool, and second, incremental migration of subsystem data from kvdb to native relational tables within LND.
• Backend Choices and Best Practices: Provides guidance on choosing between SQLite and PostgreSQL, outlines known limitations, and offers best practices for node operators, including timing, backup, and validation steps, along with implementation examples.

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[gemini-code-assist]

Code Review

This pull request introduces a comprehensive user guide for LND's database migration process. The guide is well-structured and provides valuable information for node operators planning to migrate from bbolt to a SQL backend. My review focuses on improving clarity and consistency within the document. I've pointed out a couple of typos, a grammatical issue, and some inconsistencies regarding the availability of the SQLite migration script that could confuse users. I've also suggested a minor rephrasing for better formality. Overall, this is a great addition to the documentation.

[saubyk]

/gemini review

[gemini-code-assist]

Code Review

This pull request adds a comprehensive user guide for the LND database migration process. The guide is well-structured and covers the two-stage migration from bbolt to SQL backends. My review includes a few suggestions to improve clarity, fix a broken link, and address minor formatting issues to enhance the quality of the documentation.

[saubyk]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces a new user guide for database migration in LND. The guide is well-structured and provides valuable information for node operators. I've added a few comments to improve clarity, consistency, and correctness of the examples provided.

[ellemouton]

Nice write up 🙏 a few comments

[ellemouton]

maybe use a real example like invoices & graph (since the reference to payments would at this stage be confusing)

[ellemouton]

although, there is no current planned migration between the two.. so it isnt really an interim rn

[ellemouton]

do we actually recommend this? is it not dangerous to have 2 copies of channel.db lying around? cause what if we later startup pointing to the wrong one than then broadcast invalid states?