JIRA: https://jira.spring.io/browse/INT-4394
Looks like Jackson has became much smarter and now it stores
the target type for the object, not returned interface.
We can't use Jackson annotations on the Framework classes and
we can't restrict the `messagingAwareMapper()` `ObjectMapper` just
to use fields for all the object passed through it.
As a compromise solution we shouldn't use
`Collections.unmodifiableList()` in the getter.
The copy of the internal collection is pretty enough to protect
our object from mutation.
**Cherry-pick to 4.3.x (excluding `build.gradle` change)**
# Conflicts:
# build.gradle
4f0f3d11fd