app/views/messages/_message.html.erb
<div class="message">
<%= avatar_default(message.person) %>
<div class="person">
<%= nickname(message.person) %>
</div>
<div class="content">
<%== markdown(message.content) %>
</div>
<% if message.attachments.count > 0 %>
<%= render 'messages/attachments', attachments: message.attachments %>
<% end %>
</div>