public SELF allowNullOrigin() {
        nullOriginAllowed = true;
        return self();
    }
Enables a successful CORS response with a {@code "null"} value for the CORS response header
{@code "Access-Control-Allow-Origin"}. Web browsers may set the {@code "Origin"} request header to
{@code "null"} if a resource is loaded from the local file system.

@return {@code this} to support method chaining.
core/src/main/java/com/linecorp/armeria/server/cors/AbstractCorsPolicyBuilder.java