Feature Observer IsValid

## Describe the task

Found in practice it was not uncommon to want to indirect from a featureobserver object to state, but this may not have been injected yet so should be able to report readiness/validity.
This would also apply to feature agg

Start by locating the FeatureObserver and feature aggregate entry points referenced in the issue. Read how state injection is represented and how observers currently expose state; completion should cover readiness or validity before injection and the corresponding aggregate behavior. The issue names no files or tests, so relevant coverage must be identified in the repository.

Escrita pelo modelo de indexação a partir do texto da issue.