Move Designs tab (on Issues) to CE

Renders the Discussion tab and Designs tab
in CE (as opposed to EE-only)

app/views/projects/issues/_design_management.html.haml

+- if @project.design_management_enabled?
+  #js-design-management{ data: { project_path: @project.full_path, issue_iid: @issue.iid, issue_path: project_issue_path(@project, @issue) } }
+- else
+  .mt-4
+    .row.empty-state
+      .col-12
+        .text-content
+          %h4.center
+            = _('The one place for your designs')
+          %p.center
+            - requirements_link_url = help_page_path('user/project/issues/design_management', anchor: 'requirements')
+            - requirements_link_start = '<a href="%{url}" target="_blank" rel="noopener noreferrer">'.html_safe % { url: requirements_link_url }
+            - support_link_start = '<a href="%{url}" target="_blank" rel="noopener noreferrer">'.html_safe % { url: EE::CUSTOMER_SUPPORT_URL }
+            - link_end = '</a>'.html_safe
+            = s_("DesignManagement|To enable design management, you'll need to  %{requirements_link_start}meet the requirements%{requirements_link_end}. If you need help, reach out to our %{support_link_start}support team%{support_link_end} for assistance.").html_safe % { requirements_link_start: requirements_link_start, requirements_link_end: link_end, support_link_start: support_link_start, support_link_end: link_end }
\ No newline at end of file

app/views/projects/issues/_tabs.html.haml

+%ul.nav-tabs.nav.nav-links{ role: 'tablist' }
+  %li
+    = link_to '#discussion-tab', class: 'active js-issue-tabs', id: 'discussion', role: 'tab', 'aria-controls': 'js-discussion', 'aria-selected': 'true', data: { toggle: 'tab', target: '#discussion-tab' } do
+      = _('Discussion')
+      %span.badge.badge-pill.js-discussions-count
+  %li
+    = link_to '#designs-tab', class: 'js-issue-tabs', id: 'designs', role: 'tab', 'aria-controls': 'js-designs', 'aria-selected': 'false', data: { toggle: 'tab', target: '#designs-tab', qa_selector: 'designs_tab_link' } do
+      = _('Designs')
+      %span.badge.badge-pill.js-designs-count
+.tab-content
+  #discussion-tab.tab-pane.show.active{ role: 'tabpanel', 'aria-labelledby': 'discussion' }
+    = render 'projects/issues/discussion' 
+  #designs-tab.tab-pane{ role: 'tabpanel', 'aria-labelledby': 'designs', data: { qa_selector: 'designs_tab_content'} }
+    = render 'projects/issues/design_management' 
+

app/views/projects/issues/show.html.haml

@@ -93,6 +93,6 @@
         #js-vue-discussion-filter{ data: { default_filter: current_user&.notes_filter_for(@issue), notes_filters: UserPreference.notes_filters.to_json } }
         = render 'new_branch' if show_new_branch_button?
 
-  = render_if_exists 'projects/issues/discussion'
+  = render 'projects/issues/tabs'
 
 = render 'shared/issuable/sidebar', issuable_sidebar: @issuable_sidebar, assignees: @issue.assignees