code: public CroquetRestBuilder<T> addJpaEntity(final Class<? extends Serializable> entity) {
          // check to ensure the class has the @Entity annotation
          if(entity.getAnnotation(Entity.class) == null) {
              throw new IllegalArgumentException("Only classes marked with @Entity can be added");
          }
  
          settings.getDatabaseSettings().addEntity(entity);
          return this;
      }
docs: Adds a JPA entity to Croquet.
  @param entity the entity to add.
  @return the {@link CroquetRestBuilder}.