Function verify 

pub fn verify(
    registry: &Registry,
    document: &Value,
    public_key_pem: &str,
    now: i64,
) -> Result<(), Error>

Check the RsaSignature2017 on document against public_key_pem, the key its creator names, at now (Unix seconds).

The caller has found that key, and knows whose it is; the signature says that its holder signed this document, not who the holder is.

Errors

Error::Missing when there is no RsaSignature2017, Error::Invalid when it has expired or does not verify, and otherwise why the document could not be read.