app/views/devise/mailer/confirmation_instructions.html.erb
<% require 'devise/version' %>
<p><%= t('.greeting', recipient: @resource.email) %></p>
<p><%= t('.instruction') %></p>
<p><%= link_to t('.action'), confirmation_url(@resource, confirmation_token: (Devise::VERSION.start_with?('3.') ? @token : @resource.confirmation_token)) %></p>