add comment explaining the versioned id issue with hapi client

Author: schwzr

codex-process-data-transfer/src/main/java/de/netzwerk_universitaetsmedizin/codex/processes/data_transfer/client/fhir/AbstractFhirClient.java

@@ -653,6 +653,7 @@ public void updatePatient(Patient patient)
 		Objects.requireNonNull(patient, "patient");
 
 		String id = patient.getIdElement().toVersionless().getValue();
+		// set the patient id to versionless id to workaround a `If-Match`-header bug in hapi fhir client
 		patient.setId(id);
 		logger.info("Updating patient {}", id);