Add a partial for the hash preference field

We store two settings inside a hash preference field. Solidus 2.4
is missing this partial. As will hopefully be fixed with Solidus 2.5
we load our own partial if we are using Solidus 2.4

lib/solidus_paypal_braintree/engine.rb

@@ -42,6 +42,12 @@ def self.activate
       # source form partial. This will take precedence over lib/views/backend.
       paths["app/views"] << "lib/views/backend_v1.2" if SolidusSupport.solidus_gem_version < Gem::Version.new('1.3')
 
+      # Solidus v2.4 introduced preference field partials but does not ship a hash field type.
+      # This is solved in Solidus v2.5.
+      if SolidusSupport.solidus_gem_version <= Gem::Version.new('2.5.0')
+        paths["app/views"] << "lib/views/backend_v2.4"
+      end
+
       paths["app/views"] << "lib/views/backend"
     end
   end

lib/views/backend_v2.4/spree/admin/shared/preference_fields/_hash.html.erb

@@ -0,0 +1,12 @@
+<% label = local_assigns[:label].presence %>
+<% html_options = {class: 'input_hash fullwidth'}.update(local_assigns[:html_options] || {}) %>
+
+<div class="field">
+  <% if local_assigns[:form] %>
+    <%= form.label attribute, label %>
+    <%= form.text_area attribute, html_options %>
+  <% else %>
+    <%= label_tag name, label %>
+    <%= text_area_tag name, value, html_options %>
+  <% end %>
+</div>

spec/features/backend/configuration_spec.rb

@@ -8,4 +8,15 @@
     visit "/solidus_paypal_braintree/configurations/list"
     expect(page).to have_content("Braintree Configurations")
   end
+
+  # Regression to ensure this page renders on Solidus 2.4
+  scenario 'should not raise any errors due to unavailable preference field partial' do
+    Rails.application.config.spree.payment_methods << SolidusPaypalBraintree::Gateway
+    visit '/admin/payment_methods'
+    click_link 'New Payment Method'
+    select 'Braintree', from: 'Type'
+    fill_in 'Name', with: 'Braintree Payments'
+    click_button 'Create'
+    expect(page).to have_content 'Braintree Payments'
+  end
 end