Explicit in Engagement::Update API doc that it can't be used to update relationships

engagements

#1

It’s not possible to use the update engagement API to change the engagement’s associations, but the documentation doesn’t mention this.
Actually, it even gives a link to the create engagement API “for more details about the data that can be used in engagements”, which accepts associations.

So please please please fix this doc. I just lost about one hour coding + one hour wondering why my engagements didn’t appear.