container: root: test: unit: add pluggable cases

Focuses on base pluggables, pluggable data types and functionality.

container/src/root/test/common/type.hh

@@ -39,6 +39,7 @@ namespace dfi
 //! \since docker-finance 1.0.0
 namespace tests
 {
+// TODO(afiore): move this out of common into pure unit test file
 //! \namespace dfi::tests::unit
 //! \brief docker-finance unit test cases
 //! \ingroup cpp_tests