Check validity of shapely geometries in `ShapesModel.parse()`

[LucaMarconato]

In tests/conftest.py the second multipolygon of the multipoly object is invalid, i.e.

    multipoly = GeoDataFrame(
        {
            "geometry": [
                MultiPolygon(
                    [
                        Polygon(((0, 0), (0, 1), (1, 1), (1, 0))),
                        Polygon(((0, 0), (0, -1), (-1, -1), (-1, 0))),
                    ]
                ),
                MultiPolygon(
                    [
                        Polygon(((0, 0), (0, 1), (1, 10))),
                        Polygon(((0, 0), (0, 1), (1, 1))),
                        Polygon(((0, 0), (0, 1), (1, 1), (1, 0), (1, 0))),
                    ]
                ),
            ]
        }

leads to multipoly.is_valid having False at the second entry.

This may cause subtle problems when operating on those objects; for instance this query fails:

    indices = polygons.geometry.intersects(bounding_box_non_axes_aligned)

A solution is to prevent such geometries to pass the validation step when invoking parse() and validate() in ShapesModel.