@Override
        public String toString() {
            return (dataTypeNode == null ? " unknown type" : dataTypeNode.toString()) + " " + indexingTypes.toString() + " " + (isInsideDoc ? " in document" : " in schema");
        }
FieldIndex
For storing metadata about fields.
It is owned by a SchemaIndex, so there is a one-to-one correspondence
integration/schema-language-server/language-server/src/main/java/ai/vespa/schemals/index/FieldIndex.java