As a user, when a collection contains the following documents:

[{ '_id: '1', name: 'foo' }, { _id: '2', name: 'bar' }]

and there's a unique key constraint for the "name" property. I expect
that, when trying to insert or upsert a document where the value of
"name" is already being used by an existing document in the collection,
the X Plugin will send back the same kind of error reporting the fact
that the constraint was violated.

However, currently, this is not the case, and the X Plugin is sending
back a different error, which does not contain any kind of context for
the case when an upsert actually translates to an insert and not an
update. Not sure if this is the expected behavior or not but it looks
like an inconsistency and the fact that the error does not tell the user
what actually went wrong makes it even worse.


RB: 23929
Reviewed-by: Lukasz Kotula <lukasz.kotula@oracle.com>