public CorsServiceBuilder allowNullOrigin() {
        checkState(!anyOriginSupported,
                   "allowNullOrigin cannot be enabled with any origin supported CorsService.");
        firstPolicyBuilder.allowNullOrigin();
        return this;
    }
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.
@throws IllegalStateException if {@link #anyOriginSupported} is {@code true}.
core/src/main/java/com/linecorp/armeria/server/cors/CorsServiceBuilder.java