- Introduced a feature gate mechanism to `client-go`. Depending on the actual implementation, users can control features via environmental variables or command line options. ([#122555](https://github.com/kubernetes/kubernetes/pull/122555), [@p0lyn0mial](https://github.com/p0lyn0mial))

  @Test
  fun setValidRequestMethod() {
    assertMethodForbidsRequestBody("GET")
    assertMethodPermitsRequestBody("DELETE")
    assertMethodForbidsRequestBody("HEAD")
    assertMethodPermitsRequestBody("OPTIONS")
    assertMethodPermitsRequestBody("POST")
    assertMethodPermitsRequestBody("PUT")
    assertMethodPermitsRequestBody("TRACE")
    assertMethodPermitsRequestBody("PATCH")

        .addHeader("Cache-Control: s-maxage=180")
        .addHeader("Cache-Control: max-age=60")
        .build(),
    )
  }

  @Test
  fun requestMethodOptionsIsNotCached() {
    testRequestMethod("OPTIONS", false)
  }

  @Test
  fun requestMethodGetIsCached() {
    testRequestMethod("GET", true)
  }

  @Test
  fun requestMethodHeadIsNotCached() {