Return upsertResult in the upsert function

[jvlaar]

It would be nice if the upsert() function would return a upsertResult object when called. Right now it's very hard to find out what went wrong when upsert isn't working.

https://developer.salesforce.com/docs/atlas.en-us.api.meta/api/sforce_api_calls_upsert_upsertresult.htm

[jvlaar]

I see that the call function already returns this to the upsert(), only for upsert to then ignore it.