Add the ability to natively filter geometries by the number of dimensions used by a Geometry.

[David Smith]

​PostGIS and ​SpatiaLite have a ST_NDims function which returns the number of dimensions a geometry. I propose to add a function similar to what is proposed for GeometryType in #28696.

Support for Oracle should also be possible with its GET_DIMS( ) function see ​docs . However, I couldn't find a similar function on MySQL/MariaDB.

An implementation for PostGIS/SpatiaLite would look something like this.

class NumDimensions(GeoFunc):
    function = "ST_NDims"
    output_field = IntegerField()
    arity = 1

Which would allow this to be used in QuerySets such as annotating the number of dimensions in a geometry.

Country.objects.annotate(num_dims=functions.NumDimensions("geom"))

I'll prepare a patch if accepted.

[Natalia Bidart]

PR has a an approval from Claude, but I'm setting the flag "patch needs improvement" until we clarify next steps for Oracle and potentially ​MySQL.