Allow users to manage their notifications

The user can access this page without being logged in.
We identify the user through the "subscriptions_token" parameter and
show a list of the notifications that can be enable/disable.

We will return a 404 error in case someone accesses the page with a
non-existent token.

We also control the case that some anonymous user tries to access the
page without any token, by returning the CanCan::AccessDenied exception.

spec/components/subscriptions/edit_component_spec.rb

@@ -0,0 +1,19 @@
+require "rails_helper"
+
+describe Subscriptions::EditComponent do
+  let(:user) { create(:user, subscriptions_token: SecureRandom.base58(32)) }
+  let(:component) { Subscriptions::EditComponent.new(user) }
+
+  it "renders checkboxes to change the subscriptions preferences" do
+    render_inline component
+
+    expect(page).to have_content "Notifications"
+    expect(page).to have_field "Notify me by email when someone comments on my proposals or debates",
+                                type: :checkbox
+    expect(page).to have_field "Notify me by email when someone replies to my comments", type: :checkbox
+    expect(page).to have_field "Receive by email website relevant information", type: :checkbox
+    expect(page).to have_field "Receive a summary of proposal notifications", type: :checkbox
+    expect(page).to have_field "Receive emails about direct messages", type: :checkbox
+    expect(page).to have_button "Save changes"
+  end
+end

spec/controllers/subscriptions_controller_spec.rb

@@ -0,0 +1,16 @@
+require "rails_helper"
+
+describe SubscriptionsController do
+  describe "GET edit" do
+    it "returns a 404 code with a wrong token" do
+      expect { get :edit, params: { token: "non_existent" } }.to raise_error ActiveRecord::RecordNotFound
+    end
+
+    it "doesn't allow access to anonymous users without a token" do
+      get :edit, params: { token: "" }
+
+      expect(response).to redirect_to "/"
+      expect(flash[:alert]).to eq "You do not have permission to access this page."
+    end
+  end
+end