By passing another user's GUID to the CreateOrganizationService method, we impersonated that user while executing our plugin. Alternatively, we can pass null to impersonate a System User. In this abridged example, we used a hardcoded GUID; however, typically, you will have a separate method call to resolve the GUID given a set of attributes. For example, we might resolve the GUID based on a key, the name of the user, or the role of the user.