public OAuth2TokenIntrospectionAuthorizerBuilder clientAuthentication(
            Supplier<ClientAuthentication> clientAuthenticationSupplier) {
        requireNonNull(clientAuthenticationSupplier, "clientAuthenticationSupplier");
        this.clientAuthenticationSupplier = clientAuthenticationSupplier;
        return this;
    }
Provides client authentication for the OAuth 2.0 Introspection requests, as per
<a href="https://datatracker.ietf.org/doc/html/rfc6749#section-2.3">[RFC6749], Section 2.3</a>.
oauth2/src/main/java/com/linecorp/armeria/server/auth/oauth2/OAuth2TokenIntrospectionAuthorizerBuilder.java