Summary:
The `mg_value` is the main data type used in upcoming custom procedures. Each
custom procedure will receive arguments as an array of `mg_value` instances.
The results of custom procedures will also be built as `mg_value` instances.
We should strive to have as simple and straightforward C API for custom
procedures, because we want to limit the possibility of errors and bugs on the
user facing side. Custom procedures will run in Memgraph and as such can cause
crashes and potentially a lot of nasty stuff. The burden is on the writer of
custom procedures not to mess things up, so we should make messing things up
from the C API hard if not impossible to do.
Reviewers: mferencevic, ipaljak, dsantl
Reviewed By: mferencevic
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D2443
