I have an API whose job is to aggregate resources obtained by calling multiple other APIs and then give out the aggregated response to the client. Currently even if one or more dependent API calls fail, I go ahead and aggregate response from the other dependent APIs and then give them out to the client with a 2xx status. In case all of the dependent API calls fail, I still give out a 2xx with empty list.
In case one or more dependent API calls fail, I want to give out an indication to the client. I was thinking of using the HTTP code 206. What would be the best approach to handle this scenario? Is giving out a 206 with the names of the dependent services that failed to give out a 2xx as part of a header the correct approach. If yes, what should this header be called?