fix: Remove DisallowUnknownFields from Source plugin server (#277)

See cloudquery/cloudquery#2612 for an
explanation.

Notes:
- We weren't using `DisallowUnknownFields` on the destination plugin
side
- We don't currently have a mechanism to warn about unknown fields, but
we are working on it #272
- This will unfortunately not fix plugins that have already been
released. Our next CLI release that adds new fields will have to be
breaking, but after that they can be backwards-compatible.

Author: hermanschaaf

internal/servers/source.go

@@ -61,7 +61,7 @@ func (s *SourceServer) Sync(req *pb.Sync_Request, stream pb.Source_SyncServer) e
 	var spec specs.Source
 	dec := json.NewDecoder(bytes.NewReader(req.Spec))
 	dec.UseNumber()
-	dec.DisallowUnknownFields()
+	// TODO: warn about unknown fields
 	if err := dec.Decode(&spec); err != nil {
 		return status.Errorf(codes.InvalidArgument, "failed to decode spec: %v", err)
 	}