Test if a `DiscreteDomain` contains a smaller `DiscreteDomain`

[EmilyBourne]

Occasionally algorithms need to do something slightly different along a specific point or set of points. For example at an O-point. E.g in the Poisson solver we treat the first (C+1)(C+2)/2 basis splines (eg. 3 bsplines) close to the O-point differently to the other splines. It would be useful to be able to assert that the first basis splines are on the rank where I am working as a sanity check. The method DiscreteDomain.contains only takes DiscreteElement objects which makes this check trickier. It would be nice if there was a method DiscreteDomain.contains taking a DiscreteDomain.

[tpadioleau]

Yes this can be done. We will also need to implement it for other domains. I wonder if we need cross comparisons ? Do we need to check if a DiscreteDomain contains a StridedDiscreteDomain for example ?

[EmilyBourne]

I can imagine that being useful for a sanity check