final void add(IN_NAME name, String value) {
        final NAME normalizedName = normalizeName(name);
        requireNonNull(value, "value");
        final int h = hashName(normalizedName);
        final int i = index(h);
        addAndNotify(h, i, normalizedName, value, true);
    }
Validates the given user-specified {@code value}.
core/src/main/java/com/linecorp/armeria/common/StringMultimap.java