Importing with `--store-id` leads to invalid state if store does not exist

Running fga store import with the --store-id flag will result in an incorrect state if the store does not exist.

Essentially, it'll create the authorization_model record just fine, but the store_id column will be referencing a store that does not exist. Personally, my preferred behaviour in this case would be that the store is created, but the Go SDK doesn't currently support creating a store with a preset ID, as far as I can tell.

The reason for doing so would be to allow teams using shared environment variables to have a consistent setting for the store ID, as opposed to having to change it in local development every time a new store is created - this has become a bit of a pain for us at Documatic.

Start with the fga store import path that handles --store-id, then check the Go SDK's store-creation capabilities. Reproduce the import with a nonexistent store ID and verify the result does not leave an authorization_model referencing a missing store; the intended behavior for creating a store with a preset ID still needs resolution.