feature #18197 Make Request::isFromTrustedProxy() public. (Peter Bex)

This PR was merged into the 3.1-dev branch.

Discussion
----------

Make Request::isFromTrustedProxy() public.

| Q             | A
| ------------- | ---
| Branch        | master
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

When adding custom headers to your proxy (in our particular case, a `X-Base-Url` header, but it could be anything), it is necessary to be able to tell whether the request came from a trusted proxy or not. Unfortunately, currently the `isFromTrustedProxy()` method is private, which means you'll need to subclass `Request` and add your own *differently named* method just to be able to access this information.

This functionality is pretty straightforward, and I don't see a reason to keep this method private so this a trivial pull request to make it public (and it adds a comment so it'll show up in the API docs with proper documentation).

Commits
-------

286f64f Make Request::isFromTrustedProxy() public.

src/Symfony/Component/HttpFoundation/Request.php

@@ -1931,7 +1931,15 @@ class Request
         return new static($query, $request, $attributes, $cookies, $files, $server, $content);
     }
 
-    private function isFromTrustedProxy()
+    /**
+     * Indicates whether this request originated from a trusted proxy.
+     *
+     * This can be useful to determine whether or not to trust the
+     * contents of a proxy-specific header.
+     *
+     * @return bool true if the request came from a trusted proxy, false otherwise
+     */
+    public function isFromTrustedProxy()
     {
         return self::$trustedProxies && IpUtils::checkIp($this->server->get('REMOTE_ADDR'), self::$trustedProxies);
     }