title: Django Admin: Add Action Button To Send Email
body: <p>I have a model where Mail is a Foreign Key. The user can add a mail object,I want to add a button to the change form upon clicking which the email should be sent.</p>
  <p>models.py</p>
  <pre><code>class Evaluation(models.Model):
      ...
      mail                        = models.ForeignKey(Mail, related_name=&quot;evaluation&quot;, null=True, blank=True, on_delete=models.CASCADE)
  
  </code></pre>
  <p>I possibly want the button to execute something like this:</p>
  <pre><code>def process(self):
        if self.mail is not None:
            send_mail(
                      self.mail.subject,
                      self.mail.body,
                      settings.EMAIL_HOST_USER,
                      [self.lead.user.email],
                      fail_silently=False
              )
  </code></pre>
  <p>How could I achieve the same?</p>