Add webhook templating (#23289)

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

app/views/admin/webhooks/_form.html.haml

@@ -7,5 +7,8 @@
   .fields-group
     = f.input :events, collection: Webhook::EVENTS, wrapper: :with_block_label, include_blank: false, as: :check_boxes, collection_wrapper_tag: 'ul', item_wrapper_tag: 'li'
 
+  .fields-group
+    = f.input :template, wrapper: :with_block_label, input_html: { placeholder: '{ "content": "Hello {{object.username}}" }' }
+
   .actions
     = f.button :button, @webhook.new_record? ? t('admin.webhooks.add_new') : t('generic.save_changes'), type: :submit

app/views/admin/webhooks/show.html.haml

@@ -2,14 +2,14 @@
   = t('admin.webhooks.title')
 
 - content_for :heading do
-  %h2
-    %small
-      = fa_icon 'inbox'
-      = t('admin.webhooks.webhook')
-    = @webhook.url
-
-- content_for :heading_actions do
-  = link_to t('admin.webhooks.edit'), edit_admin_webhook_path, class: 'button' if can?(:update, @webhook)
+  .content__heading__row
+    %h2
+      %small
+        = fa_icon 'inbox'
+        = t('admin.webhooks.webhook')
+      = @webhook.url
+    .content__heading__actions
+      = link_to t('admin.webhooks.edit'), edit_admin_webhook_path, class: 'button' if can?(:update, @webhook)
 
 .table-wrapper
   %table.table.horizontal-table