public ApnsServiceBuilder withCert(KeyStore keyStore, String password)
    throws InvalidSSLConfig {
        assertPasswordNotEmpty(password);
        return withSSLContext(new SSLContextBuilder()
                .withAlgorithm(KEY_ALGORITHM)
                .withCertificateKeyStore(keyStore, password)
                .withDefaultTrustKeyStore()
                .build());
    }
Specify the certificate used to connect to Apple APNS
servers.  This relies on a keystore (*.p12)
containing the certificate, along with the given password.

This library does not support password-less p12 certificates, due to a
Oracle Java library <a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6415637">
Bug 6415637</a>.  There are three workarounds: use a password-protected
certificate, use a different boot Java SDK implementation, or construct
the `SSLContext` yourself!  Needless to say, the password-protected
certificate is most recommended option.

@param keyStore  the keystore
@param password  the password of the keystore
@return  this
@throws InvalidSSLConfig if stream is invalid Keystore
 or the password is invalid
src/main/java/com/notnoop/apns/ApnsServiceBuilder.java