Fix infrastructure menu link to the first visible menu item

Current instratructure menu link is harcoded to the kubernetes
link. Nevertheless, if the kubernetes menu item can't be displayed
because the user doesn't have enough access rights, the main
menu still points to it.

We need to change that and always point to the first visible
menu item.

Changelog: fixed

lib/sidebars/projects/menus/infrastructure_menu.rb

@@ -18,7 +18,7 @@ module Sidebars
 
         override :link
         def link
-          project_clusters_path(context.project)
+          renderable_items.first.link
         end
 
         override :extra_container_html_options

spec/lib/sidebars/projects/menus/infrastructure_menu_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Sidebars::Projects::Menus::InfrastructureMenu do
+  let(:project) { build(:project) }
+  let(:user) { project.owner }
+  let(:context) { Sidebars::Projects::Context.new(current_user: user, container: project, show_cluster_hint: false) }
+
+  describe '#render?' do
+    subject { described_class.new(context) }
+
+    context 'when menu does not have any menu items' do
+      it 'returns false' do
+        allow(subject).to receive(:has_renderable_items?).and_return(false)
+
+        expect(subject.render?).to be false
+      end
+    end
+
+    context 'when menu has menu items' do
+      it 'returns true' do
+        expect(subject.render?).to be true
+      end
+    end
+  end
+
+  describe '#link' do
+    subject { described_class.new(context) }
+
+    context 'when Kubernetes menu item is visible' do
+      it 'menu link points to Kubernetes page' do
+        expect(subject.link).to eq find_menu_item(:kubernetes).link
+      end
+    end
+
+    context 'when Kubernetes menu item is not visible' do
+      before do
+        subject.renderable_items.delete(find_menu_item(:kubernetes))
+      end
+
+      it 'menu link points to Serverless page' do
+        expect(subject.link).to eq find_menu_item(:serverless).link
+      end
+
+      context 'when Serverless menu is not visible' do
+        before do
+          subject.renderable_items.delete(find_menu_item(:serverless))
+        end
+
+        it 'menu link points to Terraform page' do
+          expect(subject.link).to eq find_menu_item(:terraform).link
+        end
+      end
+    end
+
+    def find_menu_item(menu_item)
+      subject.renderable_items.find { |i| i.item_id == menu_item }
+    end
+  end
+
+  describe 'Menu Items' do
+    subject { described_class.new(context).renderable_items.index { |e| e.item_id == item_id } }
+
+    shared_examples 'access rights checks' do
+      specify { is_expected.not_to be_nil }
+
+      describe 'when the user does not have access' do
+        let(:user) { nil }
+
+        specify { is_expected.to be_nil }
+      end
+    end
+
+    describe 'Kubernetes' do
+      let(:item_id) { :kubernetes }
+
+      it_behaves_like 'access rights checks'
+    end
+
+    describe 'Serverless' do
+      let(:item_id) { :serverless }
+
+      it_behaves_like 'access rights checks'
+    end
+
+    describe 'Terraform' do
+      let(:item_id) { :terraform }
+
+      it_behaves_like 'access rights checks'
+    end
+  end
+end