Special characters in params for application proxy causing signature not to match by Andrew

Hello,

I am running an application that makes use of application proxies.  It is working great however I have recently discovered that if a param with a special character is passed to the proxy then it will cause the signature calculation and comparison to fail.

I am using the following method to compare the signatures

    query_parameters = Rack::Utils.parse_query(request.query_string)

    # Remove and save the "signature" entry
    signature = query_parameters.delete("signature")
    sorted_params = query_parameters.collect{ |k, v| "#{k}=#{Array(v).join(',')}" }.sort.join
    calculated_signature = OpenSSL::HMAC.hexdigest(OpenSSL::Digest::Digest.new('sha256'), SHOPIFY_SECRET, sorted_params)
    raise 'Invalid signature' if signature != calculated_signature

This works fine if the user visits the site at  say /apps/proxys/test or /apps/proxys/test?extra_param=english

however if the user has some additional query parameters with special characters I cannot figure out how to correctly calculate the signature /apps/proxys/test?extra_param=España.

Does anyone have any idea of how to correctly calculate a request signature for a request with special characters in the params?

Thank you very much