migrations: Update `dirty database` docs
Created by: efritz
This PR is a rough docs update on how to handle a dirty database. This PR adds a new commands sg migration add-log
, and migrator add-log
, which can be used by developers or site-admins to help resolve the dirty database conditions with the new migration infrastructure.
Reviewers: Please give special attention to the doc page and suggest where I can steal copy from other migrations work we've been doing lately.
Edit: Non-docs work was pulled out into https://github.com/sourcegraph/sourcegraph/pull/30863.