Summary:
If `capnp-id` isn't passed to LCP, then no C++ code for serialization
will be generated. Previously, only schema wasn't generated.
An error with serializing a derived class whose parent isn't serialized
is now reported with a suggestion on how to fix this.
Reviewers: mtomic, buda, msantl
Reviewed By: mtomic
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D1460