add template show api

app/controllers/templates_controller.rb

@@ -0,0 +1,5 @@
+class TemplatesController < ApplicationController
+  def show
+    @template = EcTemplate.find_by_name!(params[:name])
+  end
+end

app/views/templates/show.json.jbuilder

@@ -0,0 +1,3 @@
+json.template do
+  json.partial! 'attachments/attachment_simple', attachment: @template.attachments.last
+end

config/routes.rb

@@ -818,6 +818,7 @@ Rails.application.routes.draw do
         post :feedback
       end
     end
+    resource :template, only: [:show]
   end
 
   namespace :admins do