Autogenerate database DDL script

Problem

Right now we need to manually update the DDL script located at docs-gitlab/db/ddl.sql and docs-gitlab/db/ddl-partitions.sql whenever we add new migrations. This is a tedious and error-prone process.

Solution

Autogenerate DB DDL, refreshing the relevant scripts whenever a new migration is added. We should have a CI job that checks if the generated scripts are up to date or not.