Remove the border from the signub box on the trial registration page

- Add a simple `borderless` option we can pass through as a local
variable to the partial when we render it
- Add tests for that use case

Changelog: changed
EE: true

app/views/devise/shared/_signup_box.html.haml

 - max_first_name_length = max_last_name_length = 127
 - omniauth_providers_placement ||= :bottom
+- borderless ||= false
 
-.gl-mb-3.gl-p-4.gl-border-gray-100.gl-border-1.gl-border-solid.gl-rounded-base
+.gl-mb-3.gl-p-4{ class: (borderless ? '' : 'gl-border-gray-100 gl-border-1 gl-border-solid gl-rounded-base') }
   - if show_omniauth_providers && omniauth_providers_placement == :top
     = render 'devise/shared/signup_omniauth_providers_top'
 

ee/app/views/trial_registrations/new.html.haml

@@ -17,6 +17,7 @@
 
     .signup-page
       = render 'devise/shared/signup_box',
+        borderless: true,
         url: trial_registrations_path,
         button_text: _('Continue'),
         show_omniauth_providers: social_signin_enabled?,

spec/views/devise/shared/_signup_box.html.haml_spec.rb

@@ -63,6 +63,22 @@ RSpec.describe 'devise/shared/_signup_box' do
     end
   end
 
+  context 'using the borderless option' do
+    let(:border_css_classes) { '.gl-border-gray-100.gl-border-1.gl-border-solid.gl-rounded-base' }
+
+    it 'renders with a border by default' do
+      render
+
+      expect(rendered).to have_selector(border_css_classes)
+    end
+
+    it 'renders without a border when borderless is truthy' do
+      render('devise/shared/signup_box', borderless: true)
+
+      expect(rendered).not_to have_selector(border_css_classes)
+    end
+  end
+
   def stub_devise
     allow(view).to receive(:devise_mapping).and_return(Devise.mappings[:user])
     allow(view).to receive(:resource).and_return(spy)