FEATURE: list category moderators on the about page (#7916)

https://meta.discourse.org/t/category-group-review-moderation/116478?u=osama

spec/models/about_spec.rb

@@ -8,4 +8,46 @@ describe About do
     include_examples 'stats cachable'
   end
 
+  describe "#category_moderators" do
+    let(:user) { Fabricate(:user) }
+    let(:public_cat_moderator) { Fabricate(:user) }
+    let(:private_cat_moderator) { Fabricate(:user) }
+    let(:common_moderator) { Fabricate(:user) }
+
+    let(:public_group) do
+      group = Fabricate(:public_group)
+      group.add(public_cat_moderator)
+      group.add(common_moderator)
+      group
+    end
+
+    let(:private_group) do
+      group = Fabricate(:group)
+      group.add(private_cat_moderator)
+      group.add(common_moderator)
+      group
+    end
+
+    let!(:public_cat) { Fabricate(:category, reviewable_by_group: public_group) }
+    let!(:private_cat) { Fabricate(:private_category, group: private_group, reviewable_by_group: private_group) }
+
+    it "lists moderators of the category that the current user can see" do
+      results = About.new(private_cat_moderator).category_moderators
+      expect(results.map(&:category_id)).to contain_exactly(public_cat.id, private_cat.id)
+      expect(results.map(&:moderators).flatten.map(&:id).uniq).to contain_exactly(
+        public_cat_moderator.id,
+        common_moderator.id,
+        private_cat_moderator.id
+      )
+
+      [public_cat_moderator, user, nil].each do |u|
+        results = About.new(u).category_moderators
+        expect(results.map(&:category_id)).to contain_exactly(public_cat.id)
+        expect(results.map(&:moderators).flatten.map(&:id)).to contain_exactly(
+          public_cat_moderator.id,
+          common_moderator.id
+        )
+      end
+    end
+  end
 end