centralised migration orchestration - directly publishing to leader project

[YabMas]

This PR is part of the effort to make one region leader of the dare-migrations for all regions an app operates in (as opposed to each region orchestrating the migrations away from it).

I would have preferred to solve this on the infrastructure level. But it's surprisingly hard to forward a message from one topic to another. Not impossible, but the needed setup/resources are either unnecessarily elaborate or expensive.

So solving it in the application code isn't the most pretty but it works, so fine.

We could make the migration leader configurable in the future, but really why?

[Zatura24]

If I understand correctly you are now generating topics with different depending on the stage as well. Doesn't this lead to many topics for which you have to subscribe to them all?

[YabMas]

Stage is: test or production, so no there aren't that many topics. Maybe not the clearest var-name, wasn't sure about it but ended up going with this instead of env because that's already used a lot in our codebases with a different meaning.

[Zatura24]

Stage is: test or production, so no there aren't that many topics. Maybe not the clearest var-name, wasn't sure about it but ended up going with this instead of env because that's already used a lot in our codebases with a different meaning.

I see, if it isn't to much of a burden a more verbose environment might be better to understand in this case

[YabMas]

Sure, made the change.