RobotsTxt: specify more verbose classes

Summary:
Using PhabricatorRobotsController overwrites robots.txt for blogs, URL shortener, and CDN domains. Using [PhabricatorRobotsPlatformController](https://we.phorge.it/book/dev/class/PhabricatorRobotsPlatformController/) should fix it.

Signed-off-by: Yongmin Hong <revi@omglol.email>

Test Plan: Reload personal-phorge.revicdn.net/robots.txt and it is not verbatim copy of issuetracker.revi.xyz/robots.txt

Reviewers: #acl_sudoers, #blessed_reviewers, revi

Reviewed By: #acl_sudoers, #blessed_reviewers, revi

Differential Revision: https://issuetracker.revi.xyz/D9

.github/workflows/quicksyntaxcheck.yml

@@ -12,5 +12,7 @@ jobs:
   phpsyntax:
     runs-on: ubuntu-latest
     steps:
-      - name: PHP Basic Syntax Check
+      - name: "PHP Basic Syntax Check [robots.txt]"
         run: php -l PhabExt/PhabricatorCustomRobotsTxtController.php
+      - name: "PHP Basic Syntax Check [time.php]"
+        run: php -l time.php

PhabExt/PhabricatorCustomRobotsTxtController.php

@@ -1,6 +1,6 @@
 <?php
 
-abstract class PhabricatorRobotsController extends PhabricatorController {
+abstract class PhabricatorRobotsPlatformController extends PhabricatorRobotsController {
 
 	public function shouldRequireLogin() {
 		return false;
@@ -103,6 +103,8 @@ public function processRequest() {
 
 	$content = implode("\n", $out)."\n";
 
+	// ToDo: Cloudflare does not cache the robots.txt due to the presence of Set-Cookie.
+	// T126
 	return id(new AphrontPlainTextResponse())
 		->setContent($content)
 		->setCacheDurationInSeconds(phutil_units('2 hours in seconds'))