The raw data of the certificate or certificate chain, represented as a GenericArray of Bytes.
It should be interpreted according to cert_type.
The first certificate in this array is the server's certificate, followed by its issuer, followed by the issuer's issuer and so on.
For "x509" certificates, each certificate is an X.509 certificate in binary (DER) format.
For "pgp" certificates, each certificate is a binary OpenPGP key.