Fix lazy val serialization on case classes
Apparently there is a bug in Json4s which prevents case classes from serializing their lazy vals into JSON (https://github.com/json4s/json4s/pull/215). This has been fixed in their 3.3 branch (we are on 3.2.11 at the time of this writing) and also has been merged into Scalatra's 2.4.x branch. However, both packages have not been officially released yet and attempts to use the RC versions have not worked so far, mainly due to Scalatra's Swagger serialization module being incompatible with Json4s's.
The bug is not breaking, since all the lazy vals in our case classes can be computed from existing values. However, it would still be nicer if the client already gets this value precomputed.
So for now, we wait until we can upgrade to Scalatra 2.4 when it has been released and then later add tests to make sure the lazy vals are emitted in the JSON payloads.