private static boolean hasStructFieldsWithIndex(ImmutableSDField field) {
        return (!field.isImportedField() && field.usesStructOrMap() && hasStructFieldsWithIndex(field.getStructFields()));
    }
Validates that complex fields (of type struct or map) do not have any struct fields with 'indexing: index'.
This is not supported and will confuse the user if not validated.

Only applies for indexed search clusters.

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