@Test
  void encodedReservedPreserveSlash() {
    RequestTemplate template = new RequestTemplate();
    template.uri("/get?url={url}");
    template.method(HttpMethod.GET);
    template = template.resolve(Collections.singletonMap("url", "https://www.google.com"));
    assertThat(template.url()).isEqualToIgnoringCase("/get?url=https%3A//www.google.com");
  }
Implementations have a bug if they pass junk as the http method.
core/src/test/java/feign/RequestTemplateTest.java