REFACTOR: use rest serializer for tag-info categories

But the "synonyms" can't use the TagSerializer yet. We still have some
code from the discourse-tagging plugin that uses "text" instead of
"name", "count" instead of "topic_count", etc. We should make the js
consistent with the TagSerializer and then stop using tag_counts_json.

app/assets/javascripts/discourse/components/tag-info.js.es6

@@ -5,7 +5,6 @@ import { default as discourseComputed } from "discourse-common/utils/decorators"
 import Component from "@ember/component";
 import { reads, and } from "@ember/object/computed";
 import { isEmpty } from "@ember/utils";
-import Category from "discourse/models/category";
 
 export default Component.extend({
   tagName: "",
@@ -58,10 +57,6 @@ export default Component.extend({
           "tagInfo.synonyms",
           result.synonyms.map(s => this.store.createRecord("tag", s))
         );
-        this.set(
-          "tagInfo.categories",
-          result.category_ids.map(id => Category.findById(id))
-        );
       })
       .finally(() => this.set("loading", false))
       .catch(popupAjaxError);

app/assets/javascripts/discourse/models/store.js.es6

@@ -51,6 +51,7 @@ flushMap();
 
 export default EmberObject.extend({
   _plurals: {
+    category: "categories",
     "post-reply": "post-replies",
     "post-reply-history": "post_reply_histories",
     reviewable_history: "reviewable_histories"

app/controllers/tags_controller.rb

@@ -106,7 +106,12 @@ class TagsController < ::ApplicationController
   end
 
   def info
-    render_serialized(@tag, DetailedTagSerializer, root: :tag_info)
+    render_serialized(
+      @tag,
+      DetailedTagSerializer,
+      rest_serializer: true,
+      root: :tag_info
+    )
   end
 
   def update

test/javascripts/acceptance/tags-test.js.es6

@@ -217,6 +217,7 @@ acceptance("Tag info", {
 
     server.get("/tags/planters/info", () => {
       return helper.response({
+        __rest_serializer: "1",
         tag_info: {
           id: 12,
           name: "planters",