[OData handler] Reduce unnecessary requests for retrieving resources

[glennblock]

Given the following query

{
  me {
    drive {
      root {
        children {
          id
        }
      }
    }
  }
}

The OData handler will make multiple requests to retrieve "me", "drive", "root" and "children" entities / entitysets. In this case a single OData request can return this list with the url "https://graph.microsoft.com/v1.0/me/drive/root/children?$select=id".

In cases like this where the resource can be retrieved in a single request, that should be preferred,

[ardatan]

This might need a big refactor because GraphQL needs an object returned on each resolver on each level. Instead of having field resolvers for each field, we can analyze the upcoming GraphQL request to calculate outgoing HTTP request.