This commit adds the CDP destination APIs. Key changes include:
- use `db-migrate` for migrations
- jest for functional_tests (although I would be happy to use vitest or
alternatives if we want to, I didn't want to change too much at once)
- pnpm for package management
- koajs for the server
- Ajv for validation
- A separate PostgreSQL logical database for the destination APIs
persistence.
Things still to do:
- add some delivery mechanism that takes events from Kafka and puts
them to the destinations.
- add CI
- add to Helm Chart
- add some method of authentication. I've added the API here but it
might be that I just end up putting that in the main app in the end,
depending on how much momentum there is to try out separating the API
a bit, and the logistics of that.