anchor.diff:  keep the existing constraints and create the missing one.
   Default value is `DROP_RECREATE_QUIETLY`.
   
  -[WARNING]
  -====
  -At the moment, you must not specify the property `hibernate.transaction.jta.platform` when using Neo4j.
  -It would override Hibernate OGM's version and the transactions would not work correctly.
  -====
  -
  -[NOTE]
  -====
  -Use the following method to retrieve the transaction manager
  -(it needs to be done after the `EntityManagerFactory` has been bootstrapped):
  -
  -[source, JAVA]
  -----
  -private static TransactionManager extractJBossTransactionManager(EntityManagerFactory factory) {
  -    SessionFactoryImplementor sessionFactory =
  -        (SessionFactoryImplementor) ( (HibernateEntityManagerFactory) factory ).getSessionFactory();
  -    return sessionFactory.getServiceRegistry().getService( JtaPlatform.class ).retrieveTransactionManager();
  -}
  -----
  -====
  -
   [NOTE]
   ====
   When bootstrapping a session factory or entity manager factory programmatically,
  
positive.code: [[ogm-neo4j-transactions]]
  === Transactions
  
  [CAUTION]
  ====
  Neo4J operations must be executed inside a transaction.
  Make sure your interactions with Hibernate OGM are within a transaction when you target Neo4J.
  ====
  
  Unless a different `org.hibernate.engine.transaction.jta.platform.spi.JtaPlatform` is specified, Hibernate OGM will use a specific implementation to integrate with the Neo4j transaction mechanism.
  This means that you can start and commit transaction using the Hibernate session.
  
  The drawback is that it is not possible at the moment to let Neo4j participate in managed JTA transactions spanning several resources (see issue https://hibernate.atlassian.net/browse/OGM-370[OGM-370]).
  
  .Example of starting and committing transactions
  ====
  
negative.code: tx.commit();
  ----
  ====
  
  In the case of JTA, Hibernate OGM attaches the Neo4J internal transaction to the JTA
  transaction lifecycle.
  That way when the JTA transaction is committed or rollbacked (for example by an EJB CMT or
  explicitly), the Neo4J transaction is also committed or rollbacked.
  This makes for a nice integration in a Java EE container.
  
  [CAUTION]
  ----
  This is NOT a true JTA/XA integration but more a lifecycle alignment:
  changes on more than one datasource won't be executed as a single atomic transaction.
  
  In particular, if the JTA transaction involves multiple resources, Neo4j might commit
  before a failure of another resource. In this case, Neo4j won't be able to rollback even
  if the JTA transaction will.
  ----
  
  [[ogm-neo4j-queries]]
  === Queries
  