JPA detached entity passed to persist error

1. https://notesonjava.wordpress.com/2008/11/03/managing-the-bidirectional-relationship/
2. https://stackoverflow.com/questions/13370221/jpa-hibernate-detached-entity-passed-to-persist
3. https://github.com/SomMeri/org.meri.jpa.tutorial/blob/master/src/main/java/org/meri/jpa/relationships/entities/bestpractice/SafePerson.java
4. http://meri-stuff.blogspot.in/2012/03/jpa-tutorial.html#RelationshipsBidirectionalOneToManyManyToOneConsistency
5.