Abstract class for a revoked certificate in a CRL (Certificate Revocation List). The ASN.1 definition for revokedCertificates is:

 revokedCertificates    SEQUENCE OF SEQUENCE  {
     userCertificate    CertificateSerialNumber,
     revocationDate     ChoiceOfTime,
     crlEntryExtensions Extensions OPTIONAL
                        -- if present, must be v2
 }  OPTIONAL

 CertificateSerialNumber  ::=  INTEGER

 Extensions  ::=  SEQUENCE SIZE (1..MAX) OF Extension

 Extension  ::=  SEQUENCE  {
     extnId        OBJECT IDENTIFIER,
     critical      BOOLEAN DEFAULT FALSE,
     extnValue     OCTET STRING
                   -- contains a DER encoding of a value
                   -- of the type registered for use with
                   -- the extnId object identifier value
 }