static ClientAuthentication ofClientPassword(String clientId, String clientSecret) {
        return ofClientPassword(clientId, clientSecret, true);
    }
Returns a {@link ClientAuthentication} for the given client ID and client secret, as per
<a href="https://datatracker.ietf.org/doc/html/rfc6749#section-2.3.1">[RFC6749], Section 2.3.1</a>.
The {@link ClientAuthentication} will be encoded as the HTTP Basic authentication.
oauth2/src/main/java/com/linecorp/armeria/common/auth/oauth2/ClientAuthentication.java