uri = URI("#{ODM}/task/new/upload/#{oid}")
request = Net::HTTP::Post.new(uri)

form_data = [
  ['images', attachment.tempfile, { filename: attachment.original_filename, content_type: attachment.content_type }]
]

request.set_form form_data, 'multipart/form-data'
response = Net::HTTP.start(uri.hostname, uri.port) do |http| # pay attention to use_ssl if you need it
  http.request(request)
end

JSON.parse(response.body)