add revisions

app/controllers/templates_versions_controller.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+class TemplatesVersionsController < ApplicationController
+  load_and_authorize_resource :template
+
+  def index
+    versions = @template.template_versions.order(id: :desc).preload(:author)
+
+    render json: versions.as_json(TemplateVersions::SERIALIZE_PARAMS)
+  end
+
+  def show
+    version = @template.template_versions.find(params[:id])
+
+    render json: TemplateVersions.serialize(version)
+  end
+end