http://hl7.org/fhir/StructureDefinition/operationoutcome-message-id|5.2.0

Identifies the id of the source message used to construct the actual error message.

element_id	types
Extension
Extension.extension
Extension.url
Extension.value[x]	string
Extension
Extension.id	http://hl7.org/fhirpath/System.String
Extension.extension	Extension
Extension.url	http://hl7.org/fhirpath/System.String
Extension.value[x]	string