Update smoke test to work with one login

The smoke test needs to be smarter now that we will introduce one login.

We need to check if one login is enabled but we don't have control over
the host app, as we use a remote host, when we deploy to review we use
the review app host, same with deploying to other envs.

This commit tries to make the smoke test smarted and tests one login or
magic link depending on what is the sign up method on the host.

spec/smoke/candidate_login_spec.rb

@@ -1,12 +1,22 @@
 RSpec.describe 'Smoke test', :smoke, type: :feature do
   it 'allows new account creation' do
     when_i_go_to_the_account_creation_page
-    when_i_choose_to_create_an_account
-    then_i_can_create_an_account
 
-    when_i_type_in_my_email_address
-    and_i_click_continue
-    then_i_have_been_sent_an_email
+    if magic_link_signup?
+      when_i_choose_to_create_an_account
+      then_i_can_create_an_account
+
+      when_i_type_in_my_email_address
+      and_i_click_continue
+      then_i_have_been_sent_an_email
+    else
+      and_i_click_continue
+      then_i_am_redirected_to_one_login
+    end
+  end
+
+  def magic_link_signup?
+    page.has_content?('Do you already have an account?')
   end
 
   def when_i_go_to_the_account_creation_page
@@ -33,4 +43,8 @@ def and_i_click_continue
   def then_i_have_been_sent_an_email
     expect(page).to have_content('Check your email')
   end
+
+  def then_i_am_redirected_to_one_login
+    page.current_host == ENV.fetch('GOVUK_ONE_LOGIN_ISSUER_URL', '').chomp('/')
+  end
 end