WebClient: Send Accept-Encoding

Guzzle does not send `Accept-Encoding` header by default.
That is equivalent to sending `Accept-Encoding: *`:
https://www.rfc-editor.org/rfc/rfc9110#field.accept-encoding>
Most servers will probably return an uncompressed body
in response to that, which can be considered wasteful,
and can trigger crawler detection systems:
#1481
Others might even opt to use a compression method
that is not supported by the system
(e.g. when libcurl is not compiled with brotli support).

Let’s force Guzzle to let curl send `Accept-Encoding`
header reflecting which compression methods it supports:
guzzle/guzzle#3215

NEWS.md

@@ -39,6 +39,7 @@
 - Content Extraction spout will no longer try to extract content we have already extracted. ([#1413](https://github.com/fossar/selfoss/pull/1413))
 - Source filters are stricter, they need to start and end with a `/`. ([#1423](https://github.com/fossar/selfoss/pull/1423))
 - OPML importer has been merged into the React client. ([#1442](https://github.com/fossar/selfoss/pull/1442))
+- Web requests will send `Accept-Encoding` header. ([#1482](https://github.com/fossar/selfoss/pull/1482))
 
 ## 2.19 – 2022-10-12
 **This version requires PHP ~~5.6~~ 7.2 (see known regressions section) or newer. It is also the last version to support PHP 7.**

src/helpers/WebClient.php

@@ -62,6 +62,12 @@ public function getHttpClient(): GuzzleHttp\Client {
                 ],
                 'handler' => $stack,
                 'timeout' => 60, // seconds
+                'curl' => [
+                    // Guzzle will not send Accept-Encoding by default.
+                    // https://github.com/guzzle/guzzle/pull/3215
+                    // Delegate choosing compression method to curl.
+                    \CURLOPT_ENCODING => '',
+                ],
             ]);
 
             $this->httpClient = $httpClient;