mix ash_postgres.generate_migrations --name name_of_my_migration
1. its opt-in, if you don't like it don't use it :)
2. we don't do magic migrations. We generate a regular ecto migration from your resource changes. So you can use it as a starting point and hand edit it (and often you should or even must as we can't do things like generating data migrations).
3. you don't have to map your resources one-to-one with tables. We support multiple resources being sourced from the same table, and turning on and off migration generation per resource. It's very common to have an Ash resource backed by a postgres view, or two ash resources backed by the same table. The migration generator merges resource definitions together to create "the strictest table definition that supports both resources". You can also remap field names. So at the end of the day, you can have your cake and eat it too on that front.