Fixes #3012 - Don't display "article type" selection for customers within UI.

app/assets/javascripts/app/views/ticket_zoom/article_new.jst.eco

@@ -7,6 +7,7 @@
   <div class="editControls">
     <div class="js-avatar"></div>
     <div class="editControls-item is-hidden pop-select">
+      <% if @articleTypes.length > 1: %>
         <div class="editControls-iconHolder centered js-selectedArticleType">
           <% for articleType in @articleTypes: %>
           <div class="editControls-icon js-selectableTypes<%- ' hide' if articleType.icon != @article.icon %>" data-type="<%- articleType.name %>">
@@ -21,6 +22,7 @@
           </div>
           <% end %>
         </div>
+      <% end %>
     </div>
     <% if @internalSelector: %>
     <div class="editControls-item is-hidden js-toggleVisibility js-selectInternalPublic">

spec/system/ticket/zoom_spec.rb

@@ -1094,6 +1094,32 @@ RSpec.describe 'Ticket zoom', type: :system do
     end
   end
 
+  # https://github.com/zammad/zammad/issues/3012
+  describe 'article type selection' do
+    context 'when logged in as a customer', authenticated_as: :customer do
+      let(:customer) { create(:customer) }
+      let(:ticket)   { create(:ticket, customer: customer) }
+
+      it 'hides button for single choice' do
+        visit "ticket/zoom/#{ticket.id}"
+
+        find('.articleNewEdit-body').send_keys('Some reply')
+        expect(page).to have_no_selector('.js-selectedArticleType')
+      end
+    end
+
+    context 'when logged in as an agent' do
+      let(:ticket) { create(:ticket, group: Group.find_by(name: 'Users')) }
+
+      it 'shows button for multiple choices' do
+        visit "ticket/zoom/#{ticket.id}"
+
+        find('.articleNewEdit-body').send_keys('Some reply')
+        expect(page).to have_selector('.js-selectedArticleType')
+      end
+    end
+  end
+
   # https://github.com/zammad/zammad/issues/3260
   describe 'next in overview macro changes URL', authenticated_as: :authenticate do
     let(:next_ticket) { create(:ticket, title: 'next Ticket', group: Group.first) }