@Override
    public void applyToConfigBuilder(SchemaGeneratorConfigBuilder builder) {
        builder.forFields()
                .withEnumResolver(ConstantValueModule::extractConstantFieldValue)
                .withNullableCheck(ConstantValueModule::isNullableConstantField);
    }
Determine whether the given field is a constant (i.e. static and final) and if so, indicant whether the constant value is null.

@param field targeted field
@return true/false depending on constant value being null; otherwise returning null if field is not a constant
jsonschema-generator/src/main/java/com/github/victools/jsonschema/generator/impl/module/ConstantValueModule.java