Move webmention parsing and authorship into the app

The jonnybarnes/webmentions-parser package is now archived, and its
guzzlehttp/guzzle ^6|^7 constraint was the only thing holding Guzzle
back from 8. Port the parts we use into App\Services\WebMention and
drop the package.

Parser keeps getMentionType and the checkInReplyTo/LikeOf/RepostOf
checks unchanged. Authorship follows the same authorship algorithm,
with some fixes:

- fetch the author page with Laravel's Http client, so tests can fake
  it, and treat connection failures as AuthorshipParserException too
- keep state in locals so one instance can be reused safely
- make the url == uid == author-page check actually compare the
  h-card's uid, rather than an undefined variable

Add direct tests for both, and mark the library as archived on the
projects page.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/Services/WebMention/Parser.php

@@ -0,0 +1,86 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Services\WebMention;
+
+use App\Exceptions\InvalidMentionException;
+
+/**
+ * Inspect the parsed microformats of a webmention source.
+ *
+ * Originally from the jonnybarnes/webmentions-parser package.
+ */
+class Parser
+{
+    /**
+     * Return the type of mention.
+     *
+     * @throws InvalidMentionException when the mention type can't be determined
+     */
+    public function getMentionType(array $microformats): string
+    {
+        foreach (['in-reply-to', 'like-of', 'repost-of'] as $type) {
+            if ($this->arrayKeyExistsRecursive($type, $microformats)) {
+                return $type;
+            }
+        }
+
+        throw new InvalidMentionException;
+    }
+
+    /**
+     * Check a reply is to the intended target.
+     */
+    public function checkInReplyTo(array $microformats, string $target): bool
+    {
+        foreach ($microformats['items'] ?? [] as $item) {
+            $inReplyTo = $item['properties']['in-reply-to'] ?? null;
+            if ($inReplyTo === null) {
+                continue;
+            }
+
+            // The reply context may be an h-cite rather than a plain URL
+            if (is_array($inReplyTo[0]) && ($inReplyTo[0]['properties']['url'][0] ?? null) === $target) {
+                return true;
+            }
+
+            if (in_array($target, $inReplyTo, true)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    /**
+     * Check the microformats contain a like of the target.
+     */
+    public function checkLikeOf(array $microformats, string $target): bool
+    {
+        return in_array($target, $microformats['items'][0]['properties']['like-of'] ?? [], true);
+    }
+
+    /**
+     * Check the microformats contain a repost of the target.
+     */
+    public function checkRepostOf(array $microformats, string $target): bool
+    {
+        return in_array($target, $microformats['items'][0]['properties']['repost-of'] ?? [], true);
+    }
+
+    private function arrayKeyExistsRecursive(string $needle, array $haystack): bool
+    {
+        if (array_key_exists($needle, $haystack)) {
+            return true;
+        }
+
+        foreach ($haystack as $value) {
+            if (is_array($value) && $this->arrayKeyExistsRecursive($needle, $value)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+}