Add boundary condition side selection or removal to allow complex designs.

[wgbowley]

[wgbowley]

bit of a hack but works for most:

    @classmethod
    def is_on_axis(cls, x1: float, x2: float) -> bool:
        """ Helper function to check if a segment lies on the axis of symmetry """
        return (
            abs(x1) < 1e-7 and
            abs(x2) < 1e-7 and
            cls.problem_type == "axi"
        )