FEATURE: User fields required for existing users - Part 2 (#27172)

We want to allow admins to make new required fields apply to existing users. In order for this to work we need to have a way to make those users fill up the fields on their next page load. This is very similar to how adding a 2FA requirement post-fact works. Users will be redirected to a page where they can fill up the remaining required fields, and until they do that they won't be able to do anything else.

spec/system/user_page/user_preferences_profile_spec.rb

@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+describe "User preferences | Profile", type: :system do
+  fab!(:user) { Fabricate(:user, active: true) }
+  let(:user_preferences_profile_page) { PageObjects::Pages::UserPreferencesProfile.new }
+  let(:user_preferences_page) { PageObjects::Pages::UserPreferences.new }
+
+  before { sign_in(user) }
+
+  describe "enforcing required fields" do
+    before do
+      UserRequiredFieldsVersion.create!
+      UserField.create!(
+        field_type: "text",
+        name: "Favourite Pokemon",
+        description: "Hint: It's Mudkip.",
+        requirement: :for_all_users,
+        editable: true,
+      )
+    end
+
+    it "redirects to the profile page to fill up required fields" do
+      visit("/")
+
+      expect(page).to have_current_path("/u/bruce0/preferences/profile")
+
+      expect(page).to have_selector(
+        ".alert-error",
+        text: I18n.t("js.user.preferences.profile.enforced_required_fields"),
+      )
+    end
+
+    it "disables client-side routing while missing required fields" do
+      user_preferences_profile_page.visit(user)
+
+      find("#site-logo").click
+
+      expect(page).to have_current_path("/u/bruce0/preferences/profile")
+    end
+
+    it "allows user to fill up required fields" do
+      user_preferences_profile_page.visit(user)
+
+      find(".user-field-favourite-pokemon input").fill_in(with: "Mudkip")
+      find(".save-button .btn-primary").click
+
+      visit("/")
+
+      expect(page).to have_current_path("/")
+    end
+  end
+end