Update schemas and templates

samples/it_v1/schemas_builder/parts/maintainer.json

@@ -0,0 +1,13 @@
+{
+	"$schema": "http://json-schema.org/draft-07/schema#",
+	"properties": {
+		"maintainer": {
+			"oneOf": [
+				{"type": "string"},
+				{"enum": [
+					"''"
+				]}
+			]
+		}
+	}
+}