app/views/mailer/approval_request.html.erb
<%= render('greeting') %>
<p>
<%= t('mailer.approval_request.body_html', creator: @creator.name, href: opportunity_url(@opportunity), title: @opportunity.title) %>
</p>
<p class='centered padding'>
<a class='btn-primary' href='<%= opportunity_url(@opportunity) %>'>
<%= t('view_opportunity') %> →
</a>
</p>