http://hl7.org/fhir/StructureDefinition/contactpoint-purpose|5.2.0

Indicates the reasons that are considered appropriate to reach out to the contactable entity via this particular mechanism.  Only for use when the ContactPoint is NOT nested inside ExtendedContactDetail.
element_idtypes
Extension
Extension.extension
Extension.url
Extension.value[x]
Extension
Extension.id
Extension.extension
Extension.url
Extension.value[x]