Fixed comment replies limiting (#15217)

The limit applies to the replies relation is applies globally when
fetching a collection, which means only 3 replies in total will be
fetched across all comments.

This patches the findPage method to manually fetch the replies and
replies adjacent relations manually on each comment, applying the limit
on a comment-by-comment basis.

This is not optimised as we currently still make the initial request for
relations.

ghost/core/core/server/models/comment.js

@@ -201,6 +201,25 @@ const Comment = ghostBookshelf.Model.extend({
         return options;
     },
 
+    async findPage(options) {
+        const {withRelated} = this.defaultRelations('findPage', options);
+
+        const relationsToLoadIndividually = [
+            'replies',
+            'replies.member',
+            'replies.count.likes',
+            'replies.count.liked'
+        ].filter(relation => withRelated.includes(relation));
+
+        const result = await ghostBookshelf.Model.findPage.call(this, options);
+
+        for (const model of result.data) {
+            await model.load(relationsToLoadIndividually);
+        }
+
+        return result;
+    },
+
     countRelations() {
         return {
             replies(modelOrCollection) {