Redmine

Hi, I'm using Redmine 6.0.5 with Puma and nginx as reverse proxy on a Ubuntu 22.04 server (see also environment info below).
I would like to include a custom message in email notifications when an issue is updated to a certain status, say "In progress".
I've tried editing these two email template files:

app/views/mailer/issue_edit.html.erb
app/views/mailer/issue_edit.text.erb

.
This is the naive code I tried including in the html template, but it doesn't have any effect. The else condition is just there for trivial debugging:

<% if @journal.private_notes? %>
  (<%= l(:field_private_notes) %>) 
<% end %>
<hr />

<% if @issue.status.name == 'In progress' %>
<p>The ticket is being processed.</p>
<% else %>
<%= @issue.status.name %>
<% end %>

<ul class="journal details">
<% details_to_strings(@journal_details, false, :only_path => false).each do |string| %>
  <li><%= string %></li>
<% end %>
</ul>

<%= textilizable(@journal, :notes, :only_path => false) %>
<hr />
<%= render :partial => 'issue', :formats => [:html], :locals => { :issue => @issue, :user => @user, :issue_url => @issue_url } %>

Is there another way to do this? Considering that I really don't know Ruby, although I have some programming experience in other languages. Thanks.

Environment info:

Environment:
  Redmine version                6.0.5.stable
  Ruby version                   3.3.8-p144 (2025-04-09) [x86_64-linux]
  Rails version                  7.2.2.1
  Environment                    production
  Database adapter               PostgreSQL
  Mailer queue                   ActiveJob::QueueAdapters::AsyncAdapter
  Mailer delivery                smtp
Redmine settings:
  Redmine theme                  Bleuclair (includes JavaScript)
SCM:
  Git                            2.34.1
  Filesystem                     
Redmine plugins:
  no plugin installed