FIX: Make category-drop work with lazy_load_categories (#24187)

The category drop was rerendered after every category async change
because it updated the categories list. This is not necessary and
categories can be referenced indirectly by ID instead.

spec/models/category_spec.rb

@@ -1298,6 +1298,8 @@ RSpec.describe Category do
     let(:guardian) { Guardian.new(admin) }
     fab!(:category)
 
+    before { Category.clear_parent_ids }
+
     describe "when category is uncategorized" do
       it "should return the reason" do
         category = Category.find(SiteSetting.uncategorized_category_id)

spec/requests/api/schemas/json/category_create_response.json

@@ -79,10 +79,7 @@
           "items": {}
         },
         "has_children": {
-          "type": [
-            "string",
-            "null"
-          ]
+          "type": "boolean"
         },
         "sort_order": {
           "type": [

spec/requests/api/schemas/json/category_update_response.json

@@ -82,10 +82,7 @@
           "items": {}
         },
         "has_children": {
-          "type": [
-            "string",
-            "null"
-          ]
+          "type": "boolean"
         },
         "sort_order": {
           "type": [

spec/requests/categories_controller_spec.rb

@@ -1040,6 +1040,31 @@ RSpec.describe CategoriesController do
     end
   end
 
+  describe "#find" do
+    fab!(:category) { Fabricate(:category, name: "Foo") }
+    fab!(:subcategory) { Fabricate(:category, name: "Foobar", parent_category: category) }
+
+    it "returns the category" do
+      get "/categories/find.json",
+          params: {
+            category_slug_path_with_id: "#{category.slug}/#{category.id}",
+          }
+
+      expect(response.parsed_body["category"]["id"]).to eq(category.id)
+      expect(response.parsed_body["ancestors"]).to eq([])
+    end
+
+    it "returns the subcategory and ancestors" do
+      get "/categories/find.json",
+          params: {
+            category_slug_path_with_id: "#{subcategory.slug}/#{subcategory.id}",
+          }
+
+      expect(response.parsed_body["category"]["id"]).to eq(subcategory.id)
+      expect(response.parsed_body["ancestors"].map { |c| c["id"] }).to eq([category.id])
+    end
+  end
+
   describe "#search" do
     fab!(:category) { Fabricate(:category, name: "Foo") }
     fab!(:subcategory) { Fabricate(:category, name: "Foobar", parent_category: category) }
@@ -1066,9 +1091,8 @@ RSpec.describe CategoriesController do
       it "returns categories" do
         get "/categories/search.json", params: { parent_category_id: category.id }
 
-        expect(response.parsed_body["categories"].size).to eq(2)
+        expect(response.parsed_body["categories"].size).to eq(1)
         expect(response.parsed_body["categories"].map { |c| c["name"] }).to contain_exactly(
-          "Foo",
           "Foobar",
         )
       end