impl entities and test

storage/driver/boltdb.go

@@ -310,6 +310,14 @@ func applySet(doc, operator bson.M) (bson.M, error) {
 		if k == entity.ID {
 			continue
 		}
+		if k == "." {
+			m, ok := v.(bson.M)
+			if !ok {
+				return nil, errors.New("cannot assign non-map to doc")
+			}
+			doc = m
+			return doc, nil
+		}
 		nesting := strings.Split(k, ".")
 		if len(nesting) > 1 {
 			mInterface, ok := doc[nesting[0]]