Bunny Terraform provider: pullzone creation fails with invalid Magic Containers App ID

## What happened

Running terraform apply with the Bunny terraform provider (v0.10.3) fails when creating a bunnynet_pullzone for a Magic Containers app with: The Magic Containers App ID is not valid. The pullzone needs the container endpoint ID, which the provider did not expose as a usable value in that version.

## The fix that worked

Fixed in provider v0.15.2: you can now obtain the container endpoint ID directly, so the pullzone origin can reference it without inspecting generated resources. Maintainer rafael-at-bunny shipped the fix and updated the docs with a working example. Upgrade the provider to v0.15.2 or later.