Make sure that the Docs clarify stream length is not always plaintext length

The S3EC attempts to be as "transparent" as possible when applying client-side encryption. For example, PutObject/GetObject "just works". A deeper example is ranged gets - in Java, a ranged get request will apply to the plaintext range, the customer does not need to manually adjust the range to account for encrypted blocks.

However, there is one aspect that is seemingly not possible, which is contentLength of the GetObject stream. It includes the auth tag. Customers need to read the entire thing, which is their original message length + auth tag (or padding in the case of CBC).

This needs to be well-documented.

Commencez par la documentation des streams S3EC GetObject et de contentLength, puis vérifiez comment le chiffrement authentifié et le padding CBC affectent les octets que les clients doivent lire. Le travail est terminé lorsque la documentation distingue clairement la longueur du stream de la longueur du texte en clair d’origine et explique que le stream complet doit être lu.

Rédigé par le modèle d'indexation à partir du texte de l'issue.