message: test(ref): stabilize type
diff: @@ -312,7 +312,7 @@ it('should map options correctly on an ref-array', async () => {
  const RefArrayOptionsMappingNestedModel = getModelForClass(RefArrayOptionsMappingNested);
  const RefArrayOptionsMappingModel = getModelForClass(RefArrayOptionsMapping);
  - const schema = RefArrayOptionsMappingModel.schema;
  + const schema: mongoose.Schema = RefArrayOptionsMappingModel.schema; // the definition ":mongoose.Schema" is there, because `.schema` is somehow "any"
  expect(RefArrayOptionsMappingNestedModel.schema.path('dummy')).toBeInstanceOf(mongoose.Schema.Types.String);
  