add @Transient to AbstractPersistableCustom isNew()

see https://jira.spring.io/browse/DATAJPA-622

Even though we don't use Hibernate, copying this annotation from the
original class in Spring Data seems prudent - just in case.  It should
not cause any harm or side effects on OpenJPA.

fineract-provider/src/main/java/org/apache/fineract/infrastructure/core/domain/AbstractPersistableCustom.java

@@ -23,6 +23,7 @@ import javax.persistence.GeneratedValue;
 import javax.persistence.GenerationType;
 import javax.persistence.Id;
 import javax.persistence.MappedSuperclass;
+import javax.persistence.Transient;
 import org.springframework.data.domain.Persistable;
 
 /**
@@ -55,6 +56,7 @@ public abstract class AbstractPersistableCustom<PK extends Serializable> impleme
     }
 
     @Override
+    @Transient // DATAJPA-622
     public boolean isNew() {
         return null == this.id;
     }