The negate field doesn't get used, which means you cant exclude tags (#…

…3713)

e.g. This allows you to

`/api/posts?sort=-createdAt&filter[tag]=14` to include tag 14 and `/api/posts?sort=-createdAt&filter[tag]=-14` to exclude tag 14

extensions/tags/src/Filter/PostTagFilter.php

@@ -23,6 +23,6 @@ public function filter(FilterState $filterState, string $filterValue, bool $nega
     {
         $filterState->getQuery()
             ->join('discussion_tag', 'discussion_tag.discussion_id', '=', 'posts.discussion_id')
-            ->where('discussion_tag.tag_id', $filterValue);
+            ->where('discussion_tag.tag_id', $negate ? '!=' : '=', $filterValue);
     }
 }