We have issues regarding the config.json file when developing journey builder custom activity. The background is, salesforce marketing cloud SMS is not supported, hence, we have to build a new custom activity for SMS sending within Journey builder. We have to pass audience information(e.g. Name, Mobile Number) and activity configuration(e.g. SMS template) to the SMS interface we are leveraging. However, we find that we cannot dynamically pass audience attributes to the SMS interface. For example: we want to pass 'Name' and 'Mobile' to the interface and we have two DEs, one is called DE1, the other one is called DE2, both of them have name and mobile number fields. When user using DE1 as journey entry, the attributes should come from DE1, likewise, when DE2 is used as a journey entry, the attributes should come from DE2. We know how to setup config.json - inArguments,Wbut we don't know know how to do dynamic binding in config.json - inArguments, rather than static binding.