Eadg integral on part of the boundary

[dokken]

@WjjSteve

inner_facets = mesh.locate_entities_boundary(msh, 1,  boundary_marker)
facet_tags = mesh.meshtags(msh, 1, inner_facets, np.full(len(inner_facets), 1))
ds = ufl.Measure("ds", domain=msh, subdomain_data=inner_facets, subdomain_id=facet_tags)

It should be like

marker_value = 33
inner_facets = mesh.locate_entities_boundary(msh, 1,  boundary_marker)
facet_tags = mesh.meshtags(msh, 1, inner_facets, np.full(len(inner_facets), marker_value, dtype=np.int32))
ds = ufl.Measure("ds", domain=msh, subdomain_data=facet_tags, subdomain_id=marker_value)