Fix mark as featured button being rendered to everyone

We introduced this issue in commit f8faabf7d.

Since this component didn't have any tests (there are system tests for
it, though), we're also adding tests that check that only the right
buttons are rendered when accessing as administrator.

app/components/debates/mark_featured_action_component.rb

@@ -6,7 +6,7 @@ class Debates::MarkFeaturedActionComponent < ApplicationComponent
     @debate = debate
   end
 
-  def render
+  def render?
     can? :mark_featured, debate
   end
 end

spec/components/debates/mark_featured_action_component_spec.rb

@@ -0,0 +1,31 @@
+require "rails_helper"
+
+describe Debates::MarkFeaturedActionComponent do
+  let(:debate) { create(:debate) }
+
+  it "is not rendered for regular users" do
+    sign_in(create(:user, :verified))
+
+    render_inline Debates::MarkFeaturedActionComponent.new(debate)
+
+    expect(page).not_to be_rendered
+  end
+
+  context "administradors", :admin do
+    it "renders a button to mark debates as featured" do
+      render_inline Debates::MarkFeaturedActionComponent.new(debate)
+
+      expect(page).to have_button "Featured"
+      expect(page).to have_button count: 1
+    end
+
+    it "renders a button to unmark featured debates" do
+      debate = create(:debate, featured_at: Time.current)
+
+      render_inline Debates::MarkFeaturedActionComponent.new(debate)
+
+      expect(page).to have_button "Unmark featured"
+      expect(page).to have_button count: 1
+    end
+  end
+end