Workspace template & DB init generation from migrations

[ShreyBana]

Today, if a migration is supposed to be ran for a workspace, it has to be manually copied to the workspace creation template. It would be nice if the template would get automatically generated from the necessary migrations. For something like this, we might have to refactor our migration directory to make it easy to write an automated step. Maybe split them out into migrations/superposition & migrations/workspace. We can extend this to generate a DB init script as well.