FEATURE: the ability to change the order of flags (#27269)

Continued work on moderate flags UI.
In this PR admins are allowed to change the order of flags. The notify user flag is always on top but all other flags can be moved.

spec/services/reorder_flag_spec.rb

@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+
+RSpec.describe(ReorderFlag) do
+  subject(:result) do
+    described_class.call(flag_id: flag.id, guardian: current_user.guardian, direction: direction)
+  end
+
+  let(:flag) { Flag.order(:position).last }
+  let(:direction) { "up" }
+
+  context "when user is not allowed to perform the action" do
+    fab!(:current_user) { Fabricate(:user) }
+
+    it { is_expected.to fail_a_policy(:invalid_access) }
+  end
+
+  context "when direction is invalid" do
+    fab!(:current_user) { Fabricate(:admin) }
+    let(:direction) { "side" }
+
+    it { is_expected.to fail_a_contract }
+  end
+
+  context "when move is invalid" do
+    fab!(:current_user) { Fabricate(:admin) }
+    let(:direction) { "down" }
+
+    it { is_expected.to fail_a_policy(:invalid_move) }
+  end
+
+  context "when user is allowed to perform the action" do
+    fab!(:current_user) { Fabricate(:admin) }
+
+    it "sets the service result as successful" do
+      expect(result).to be_a_success
+    end
+
+    it "moves the flag" do
+      expect(Flag.order(:position).map(&:name)).to eq(
+        %w[notify_user notify_moderators off_topic inappropriate spam illegal],
+      )
+      result
+      expect(Flag.order(:position).map(&:name)).to eq(
+        %w[notify_user notify_moderators off_topic inappropriate illegal spam],
+      )
+    end
+
+    it "logs the action" do
+      expect { result }.to change { UserHistory.count }.by(1)
+      expect(UserHistory.last).to have_attributes(
+        custom_type: "move_flag",
+        details: "flag: #{result[:flag].name}\ndirection: up",
+      )
+    end
+  end
+end