Fix timestamp serialization for run action

As far as I remember, the timestamp is not really used in the frontend (but in the backend). Still, it should be fixed to provide correct data and avoid confusion.

Author: MrSerth

app/controllers/submissions_controller.rb

@@ -415,7 +415,11 @@ def send_and_store(client_socket, message)
                           end
     @testrun[:messages].push message
     @testrun[:status] = message[:status] if message[:status]
-    client_socket&.send_data(message.to_json)
+
+    # Workaround for the undesired serialization of ActiveSupport::Duration (just `to_i` rather than `to_f`)
+    message_serialized = message.dup
+    message_serialized[:timestamp] = message_serialized[:timestamp].to_f
+    client_socket&.send_data(message_serialized.to_json)
   end
 
   def max_output_buffer_size