Returned when a DSL feature is recognized but not yet implemented.
The feature field names the unsupported feature.
The planned_for field indicates the target release.
Examples
iex> uf = %ExDatalog.UnsupportedFeature{feature: :aggregates, planned_for: "v0.6.0"}
iex> uf.feature
:aggregates
iex> uf.planned_for
"v0.6.0"