Fix Reference Key columns persistence issue in db

Fix Reference Key columns persistence issue in db

Problem: When PfReferenceTimestamp Key is persisted in db, the parent
class fields are ignored which causes inconsistent data while saving and
fetching in db.

Fix: JPA is not supporting inheritance in @Embeddable classes. Hence
included the super class as @Embedded property in PfReferenceTimestamp
key. @Embedded properties are unable to be queried directly. Slightly
modified Dao methods to support querying @embedded fields.

Issue-ID: POLICY-3049
Signed-off-by: zrrmmua <ramesh.murugan.iyer@est.tech>
Change-Id: I5c2e03a5ae98525764a64dd6cce1a1298c5f9816