Normalize model instances with default values
Normalize model instances with default values

Bug:
If a model is not built the same way on different api calls, then there
is a chance that expected fields are missing. For instance, when we
request comments via the comments page, we add the `loadMoreIds` field
manually since the data necessary to make this field exists in the
response. In the case of posting a reply, that same data is not there
since you get a singular reply back and therefore that field is not
added.

Since our store adds this incomplete reply to the comments state, this
can actually break views that expect the `loadMoreIds` field to be
there.

Fix:
This iterates through the model's `PROPERTIES` and adds any missing
fields with default values.

Testing:
I spot checked this across the mweb app and didn't experience any
problems.

reddit/node-api-client,reddit/snoode