Inject 'provisional_communities' key to ES index.

def inject_provisional_community(sender, json=None, record=None, index=None,
                                 **kwargs):
    """Inject 'provisional_communities' key to ES index."""
    if index and not index.startswith(
            current_app.config['COMMUNITIES_INDEX_PREFIX']):
        return

    json['provisional_communities'] = list(sorted([
        r.id_community for r in InclusionRequest.get_by_record(record.id)
    ]))