Manifest Collision

When the ProfilePayloads framework import manifests, it does not allow multiple manifests for a single domain in a given source type.

This means that if multiple versions of a manifest for a domain is loaded, it must select only one to use.

These are the steps the framework uses to decide which manifest to use:

1. The manifest file with the highest integer value for the pfm_version key is used.
2. The manifest file with the later date value for the pfm_last_modified key is used.