http://hl7.org/fhir/StructureDefinition/operationoutcome-issue-source|5.2.0

Identifies the logical module/software section responsible for identifying the issue.
typedestination
baseDefinitionhttp://hl7.org/fhir/StructureDefinition/Extension
typehttp://hl7.org/fhir/StructureDefinition/Extension
Extension.value[x].typehttp://hl7.org/fhir/StructureDefinition/string