Pull request: all: imp http handlers, imp docs

Merge in DNS/adguard-home from fix-openapi to master

Squashed commit of the following:

commit 0e7530472fb566e5cab73d178c8ec16e5ef11dcb
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Wed Jan 13 17:02:06 2021 +0300

    all: imp http handlers, imp docs

internal/home/authglinet_test.go

@@ -36,7 +36,7 @@ func TestAuthGL(t *testing.T) {
 		binary.BigEndian.PutUint32(data, tval)
 	}
 	assert.Nil(t, ioutil.WriteFile(glFilePrefix+"test", data, 0o644))
-	r, _ := http.NewRequest("GET", "http://localhost/", nil)
+	r, _ := http.NewRequest(http.MethodGet, "http://localhost/", nil)
 	r.AddCookie(&http.Cookie{Name: glCookieName, Value: "test"})
 	assert.True(t, glProcessCookie(r))
 	GLMode = false