Vector tiles buffer is used to include data that is just outside of the tile. This data is used to prevent border effects when rendering the geometries. It is currently [hardcoded to 5 pixels](https://github.com/elastic/elasticsearch/blob/de2781f98696c1e6cfad2b5bf46fe752a5e3edbb/x-pack/plugin/vector-tile/src/main/java/org/elasticsearch/xpack/vectortile/feature/FeatureFactory.java#L63) but it should probably need to be user configurable by adding a new property on the vector tiles API which can change the value.




x-pack/plugin/vector-tile/src/main/java/org/elasticsearch/xpack/vectortile/rest/VectorTileRequest.java
SearchSourceBuilder.AGGS_FIELD,
            ObjectParser.ValueType.OBJECT
        );
        PARSER.declareField(
            VectorTileRequest::setSortBuilders,
            SortBuilder::fromXContent,
            SearchSourceBuilder.SORT_FIELD,
            ObjectParser.ValueType.OBJECT_ARRAY
        );
        
        PARSER.declareString(VectorTileRequest::setGridAgg, GRID_AGG_FIELD);
        PARSER.declareInt(VectorTileRequest::setGridPrecision, GRID_PRECISION_FIELD);
        PARSER.declareString(VectorTileRequest::setGridType, GRID_TYPE_FIELD);
        PARSER.declareInt(VectorTileRequest::setExtent, EXTENT_FIELD);
        PARSER.declareBoolean(VectorTileRequest::setExactBounds, EXACT_BOUNDS_FIELD);
        PARSER.declareField(VectorTileRequest::setTrackTotalHitsUpTo, (p) -> {
            XContentParser.Token token = p.currentToken();
            if (token == XContentParser.Token.VALUE_BOOLEAN
                || (token == XContentParser.Token.VALUE_STRING && Booleans.isBoolean(p.text()))) {
                return p.booleanValue() ? TRACK_TOTAL_HITS_ACCURATE : TRACK_TOTAL_HITS_DISABLED;
            } else {
                return p.intValue();
            }
        }, SearchSourceBuilder.TRACK_TOTAL_HITS_FIELD, ObjectParser.ValueType.VALUE);
    }
    static VectorTileRequest parseRestRequest(RestRequest restRequest) throws IOException {
        final VectorTileRequest request = new VectorTileRequest(
            Strings.splitStringByCommaToArray(restRequest.param(INDEX_PARAM)),
            restRequest.param(FIELD_PARAM),
            Integer.parseInt(restRequest.param(Z_PARAM)),