void tagOwner(ParsedDocument document) {
        verifyThat(ownedBy == null, "already owned by document "+ownedBy);
        this.ownedBy = document;
    }
This class holds the extracted information after parsing a "struct"
block, using simple data structures as far as possible.  Do not put
advanced logic here!
@author arnej27959
config-model/src/main/java/com/yahoo/schema/parser/ParsedStruct.java