xmlunit 2.1.0 is the latest release for xmlunit.
Most of the xmlunit functionality used within spring-framework
was done through the xmlunit 1.x helper class
`org.custommonkey.xmlunit.XMLAssert`.
As of xmlunit 2.0.0 most of the XML comparison methods are done
through hamcrest matchers exposed by the xmlunit-matchers
library. In some cases during the migration, the matchers
had to be customized with custom `NodeMatcher` or
`DifferenceEvaluator` instances in order to keep the assertions
correct (they were performed with xmlunit 1.x previously).
Issue: SPR-14043