Adding upstream version 0.28.1.

Signed-off-by: Daniel Baumann <daniel@debian.org>

core/collection_model_base_options.go

@@ -0,0 +1,11 @@
+package core
+
+var _ optionsValidator = (*collectionBaseOptions)(nil)
+
+// collectionBaseOptions defines the options for the "base" type collection.
+type collectionBaseOptions struct {
+}
+
+func (o *collectionBaseOptions) validate(cv *collectionValidator) error {
+	return nil
+}