stellar-xdr's StringM::from_str bypasses max length validation
StringM::from_str does not validate that the input length is within the declared maximum (MAX). Calling StringM::<N>::from_str(s) where s is longer than N bytes succeeds and returns an Ok value instead of Err(Error::LengthExceedsMax), producing a StringM that violates its length invariant. This affects any code that constructs StringM values from string input using FromStr (including str::parse), and relies on the type's maximum length constraint being enforced. An oversized StringM could propagate …