Lets a dump page list the dumps related to it. It adds dump_backlinks,
which records the links from a dump's note or comments to other dumps and
which backlink-service fills, and an index on dumps.url to find the dumps
an external link was posted as.
f
up(db: DatabaseSync): void
Run once by runMigrations. It doesn't scan the notes and comments already
posted, so their links are recorded only once they are edited.
Usage
import * as mod from "api/db/migrations/0003_dump_backlinks.ts";