private GrantedOAuth2AccessTokenBuilder rawResponse(String rawResponse) {
        this.rawResponse = requireNonNull(rawResponse, "rawResponse");
        return this;
    }
An {@link Iterable} of extra system-specific token parameters included with Access Token Response,
OPTIONAL.
oauth2/src/main/java/com/linecorp/armeria/common/auth/oauth2/GrantedOAuth2AccessTokenBuilder.java