@simong should this function be removed? TBH I'm not a big fan of the contract of this method, I'm not sure why adding `optionalKey` and `previousValue` is made a part of a serialization method. Shouldn't there be something like an "update" method instead?

The awkwardness is apparent in oae-config/lib/api.js where you need to take an object, serialize it with the update and then deserialize it right after so you can add another.