private static String validateComplexFields(Schema schema) {
        return schema.allFields()
                .filter(field -> isUnsupportedComplexField(field))
                .map(ComplexFieldsWithStructFieldAttributesValidator::toString)
                .collect(Collectors.joining(", "));
    }
Validates that complex fields (of type struct or map) that have struct field attributes are supported.

Only applies for indexed search clusters.

@author geirst
config-model/src/main/java/com/yahoo/vespa/model/application/validation/ComplexFieldsWithStructFieldAttributesValidator.java