I upsert into Contact with external id using REST API like this :
I send PATCH request along with Contact json data. It works just fine, and creates an orphaned Contact record since I don't include AccountId. I don't send AccountId because I do not have AccountId in my database.
But I do have external id field in Account that I can lookup in Account to find AccountId that I want to relate the Contact being upserted.
But I believe it'll require me to send two API requests, one to lookup AccountId in Account using external id, then upsert into Contact passing retrieved AccountId.
What's the best way for me to upsert into Contact without looking up AccountId, therefore, saving me a API call?