Modify the application context's internal bean factory after its standard
initialization. All bean definitions will have been loaded, but no beans
will have been instantiated yet. This allows for overriding or adding
properties even to eager-initializing beans.
Invoked right at the end of the singleton pre-instantiation phase,
with a guarantee that all regular singleton beans have been created
already. ListableBeanFactory.getBeansOfType(java.lang.Class<T>) calls within
this method won't trigger accidental side effects during bootstrap.
NOTE: This callback won't be triggered for singleton beans
lazily initialized on demand after BeanFactory bootstrap,
and not for any other bean scope either. Carefully use it for beans
with the intended bootstrap semantics only.