feat: join field works with hasMany relationships (#8493)

Join field works on relationships and uploads having `hasMany: true`

---------

Co-authored-by: Sasha <64744993+r1tsuu@users.noreply.github.com>

test/joins/collections/Categories.ts

@@ -49,6 +49,12 @@ export const Categories: CollectionConfig = {
       collection: postsSlug,
       on: 'category',
     },
+    {
+      name: 'hasManyPosts',
+      type: 'join',
+      collection: postsSlug,
+      on: 'categories',
+    },
     {
       name: 'group',
       type: 'group',