Add explanation as to if and when it is acceptable to bundle Patient Resources in ITI-65

[simoneOnFhir]

The MHD Spec is unclear as to whether Submitting DocumentReferences with bundles Patients is allowed.

There is an example showing this, but the verbage is a bit unclear:
"Patient would typically only be allowed by the Document Recipient in PUSH interaction situations, but may be accepted for other reasons at the discretion of the Document Recipient actor policy."
https://profiles.ihe.net/ITI/MHD/ITI-65.html#23654121-bundle-resources

Apparently this refers to "Bundled Patients" but the sentence above is very ambiguous.
Also it is not clear, what constitutes a "PUSH interaction situation" and whether this is within the scope of ITI-65 or not.

see Zulip discussion: https://chat.fhir.org/#narrow/stream/179223-ihe/topic/MHD.20bundled.20vs.2E.20contained.20Patient

[JohnMoehrke]

Agree wit the need. I welcome recommended text changes to make these points more clear.

[JohnMoehrke]

do we need to allow for subject.identifier and not subject.reference? such as for regions with a national identifier?