@SuppressWarnings("unchecked")
  private void addPhone(String key, Telephone telephone, Map<String, Object> map) {
    List<String> collection = (List<String>) map.computeIfAbsent(key, k -> new ArrayList<>());
    collection.add(telephone.getText());
  }
Maps from a VCard to a Microsoft Graph contacts resource as defined by
https://developer.microsoft.com/en-us/graph/docs/api-reference/v1.0/resources/contact.
extensions/data-transfer/portability-data-transfer-microsoft/src/main/java/org/datatransferproject/transfer/microsoft/transformer/contacts/ToGraphContactTransformer.java