@Override
    public String toString() {
        final String value = asHeaderValue();
        return value.isEmpty() ? (getClass().getSimpleName() + "(<empty>)")
                               : (getClass().getSimpleName() + '(' + value + ')');
    }
Returns a new {@link StringBuilder} with the common directives appended.
Note that the first two characters ({@code ", "} must be stripped.
core/src/main/java/com/linecorp/armeria/common/CacheControl.java