Currently, DisjointUnionEnumeratedSets has an option to be a facade parent, but the category framework, and hence the coercion framework, does not know it is a facade parent. This can lead to test suite failures and some other unexpected behaviors, such as not being able to create elements. In particular, this causes problems noted on #22029.

CC: @jdemeyer @mezzarobba @nthiery

Component: categories

Author: Travis Scrimshaw

Branch/Commit: 5c4716b

Reviewer: Andrew Mathas, Frédéric Chapoton

Issue created by migration from https://trac.sagemath.org/ticket/22382