Enhance toString methods in factory classes

Enhance toString methods in factory classes

The factory classes in policy-endpoints have toString() methods that
return "[]" for their list contents.  Updated the code to provide a list
of the keys rather than just an empty list.
Also replaced some toString() methods with lombok.
Also replace StringBuilder with concatenation in some cases.

Issue-ID: POLICY-3298
Change-Id: I64fca21a4b009f7e09fcc482b5d156753fb7e680
Signed-off-by: Jim Hahn <jrh3@att.com>