app/views/advertisement_previews/index.html.erb
<html lang="en">
<head>
<style>
* { font-family: system-ui; }
li { margin-bottom: 5px; }
</style>
</head>
<body>
<h1>Preview ads for all active campaigns</h1>
<ul>
<% @campaigns.each_with_index do |campaign, index| %>
<li><%= index + 1 %>. <%= link_to "#{campaign.id}: Preview ads for #{campaign.organization.name} #{campaign.name}", advertisement_preview_path(campaign) %></li>
<% end %>
</ul>
</body>