Apparently, you can't add a table to a publication if its schema is
already part of the publication (and vice versa), e.g.,
=# alter publication p1 add table s1.t1;
ERROR: 22023: cannot add relation "s1.t1" to publication
DETAIL: Table's schema "s1" is already part of the publication or part
of the specified schema list.
Is there a reason for this? It looks a bit like a misfeature to me. It
constrains how you can move your tables around between schemas, based on
how somewhere else a publication has been constructed.
It seems to me that it shouldn't be difficult to handle the case that a
table is part of the publication via two different routes. (We must
already handle that since a subscription can use more than one publication.)
