Download active_storage blobs through proxy

app/lib/active_storage/service/ds_proxy_service.rb

@@ -25,6 +25,29 @@ module ActiveStorage
 
     private
 
+    def object_for(key, &block)
+      blob_url = url(key)
+      if block_given?
+        request = Typhoeus::Request.new(blob_url)
+        request.on_headers do |response|
+          if response.code != 200
+            raise Fog::OpenStack::Storage::NotFound.new
+          end
+        end
+        request.on_body do |chunk|
+          yield chunk
+        end
+        request.run
+      else
+        response = Typhoeus.get(blob_url)
+        if response.success?
+          response
+        else
+          raise Fog::OpenStack::Storage::NotFound.new
+        end
+      end
+    end
+
     def publicize(url)
       search = %r{^https://[^/]+/v1/AUTH_[a-f0-9]{32}}
       replace = 'https://static.demarches-simplifiees.fr'