This change accomplishes 3 things related to the defaults member for

models.
First, it fixes up the typing for the defaults definitions in all the

models that we've implemented so far to be Result<Partial<AttrsType>>.
Second, for things that inherit from base classes, we now rely on

automerge instead of manually calling _.defaults().
Finally, we had a few instances where the defaults were including

objects or arrays but were implemented as a plain object instead of a

function. We've had problems in the past where these weren't deep

copied, and multiple objects ended up sharing the same object or array

value. These have been fixed up to always be a function that returns new

data.

Ran js-tests.