Fixes #33691 - Make webhook templates preview work

app/controllers/webhook_templates_controller.rb

@@ -2,4 +2,43 @@
 
 class WebhookTemplatesController < TemplatesController
   include ForemanWebhooks::Controller::Parameters::WebhookTemplate
+
+  def preview
+    if params[:id]
+      find_resource
+    else
+      @template = resource_class.new(params[type_name_plural])
+    end
+    @template.template = params[:template]
+    # TODO: update for multiple events when webhooks support multiple events
+    id_event_model = @template.webhooks.map { |webhook| { webhook_id: webhook.id, event_name: webhook.events.first } }
+                              .uniq { |id_event| id_event[:event_name] }.map do |id_event|
+      # TODO: This could be id_event => { webhook_id:, event_name: }
+      webhook_id = id_event[:webhook_id]
+      event_name = id_event[:event_name]
+      model = event_name.delete_suffix(Webhook::EVENT_POSTFIX).rpartition('_').first.tr('.', '/').classify.safe_constantize
+      next unless model
+
+      { webhook_id: webhook_id, event_name: event_name, model: model }
+    end.compact.sample
+
+    # TODO: This could be id_event_model => { webhook_id:, event_name:, model: }
+    webhook_id = id_event_model[:webhook_id]
+    event_name = id_event_model[:event_name]
+    model = id_event_model[:model]
+    # TODO: Find a way to get a sample for Actions
+    # RANDOM() works only on PostgreSQL
+    object = model < ApplicationRecord ? model.order("RANDOM()").limit(1).first : model
+    context = ::Logging.mdc.context.symbolize_keys
+    # TODO: Waits for Ruby 3.1+ syntax
+    variables = {
+      event_name: event_name,
+      object: object,
+      context: context,
+      payload: { object: object, context: context },
+      webhook_id: webhook_id,
+    }
+    renderer = params.delete('force_safemode') ? Foreman::Renderer::SafeModeRenderer : Foreman::Renderer
+    safe_render(@template, Foreman::Renderer::PREVIEW_MODE, renderer, escape_json: true, variables: variables)
+  end
 end

app/models/webhook_template.rb

@@ -60,6 +60,6 @@ def support_single_host_render?
   end
 
   def support_preview?
-    false
+    webhooks.any?
   end
 end