def METHOD_NAME(obj, eng):
    """Merge two articles.
    The workflow payload is overwritten by the merged record, the conflicts are
    stored in ``extra_data.conflicts``. Also, it adds a ``callback_url`` which
    contains the endpoint which resolves the merge conflicts.
    Note:
        When the feature flag ``FEATURE_FLAG_ENABLE_MERGER`` is ``False`` it
        will skip the merge.
    """
    if not current_app.config.get('FEATURE_FLAG_ENABLE_MERGER'):
        return None
    matched_control_number = obj.extra_data['matches']['approved']
    update = obj.data
    update_source = LiteratureReader(obj.data).source
    if current_app.config.get('FEATURE_FLAG_ENABLE_HEP_REST_RECORD_PULL'):
        record_data = get_record_from_hep("lit", matched_control_number)
        head_uuid = record_data['uuid']
        head_record = record_data['metadata']
        head_revision_id = record_data['revision_id']
        head_version_id = head_revision_id + 1
    else:
        head_uuid = PersistentIdentifier.get(
            'lit', matched_control_number).object_uuid
        head_record = InspireRecord.get_record(head_uuid)
        head_version_id = head_record.model.version_id
        head_revision_id = head_record.revision_id
        head_record = head_record.to_dict()
    head_root = read_wf_record_source(record_uuid=head_uuid, source=update_source.lower())
    # TODO: remove check when we'll use hep on prod
    if current_app.config.get('FEATURE_FLAG_USE_ROOT_TABLE_ON_HEP'):
        head_root = deepcopy(head_root['json'] if head_root else {})
    else:
        head_root = deepcopy(head_root.json if head_root else {})
    obj.extra_data['head_uuid'] = str(head_uuid)
    obj.extra_data['head_version_id'] = head_version_id
    obj.extra_data['merger_head_revision'] = head_revision_id
    obj.extra_data['merger_original_root'] = head_root
    merged, conflicts = merge(
        head=head_record,
        root=head_root,
        update=update,
    )
    obj.data = merged
    if conflicts:
        obj.extra_data['conflicts'] = conflicts
        obj.extra_data['conflicts_metadata'] = {
            'datetime': datetime.now().strftime("%b %d, %Y, %H:%M:%S %p"),
            'update_source': update_source,
        }
        obj.extra_data['callback_url'] = \
            get_resolve_merge_conflicts_callback_url()
    obj.save()