- Improved the check for "how to join from A to B" such that when

- Improved the check for "how to join from A to B" such that when
a table has multiple, composite foreign keys targeting a parent table,
the :paramref:`.relationship.foreign_keys` argument will be properly
interpreted in order to resolve the ambiguity; previously this condition
would raise that there were multiple FK paths when in fact the
foreign_keys argument should be establishing which one is expected.
fixes #2965