`scale` arg as a dolfinx.fem.Constant?

[pierricmora]

Hi and thanks a lot for this library.

I was wondering whether there could be any plan to tolerate the scale parameter in create_periodic_constraint_geometrical / topological to be of type dolfinx.fem.Constant and then be updatable without re-compilation, the same way dolfinx.fem.dirichletbc works. As a piece of context I am implementing Floquet-Bloch periodic BCs: the scale parameter is $\exp(ikL)$ with $k$ a parameter (the wavenumber), over which I loop. As is I have to create the mpc and call finalize() at each iteration.