Catch bad "To:" in mails (#748)

I don't like receiving every other day a monstruosity like:
> [see the PR description for example content]
Instead of an infinitely clearer straight-to-the-point one-liner that
wouldn't mess around with our logs monitoring:
>uvicorn.error - ERROR - Bad email adress: "". For mail with subject
"MyECL - reset your password".

Author: Marc-Andrieu

app/utils/mail/mailworker.py

@@ -40,4 +40,9 @@ def send_email(
     with smtplib.SMTP(settings.SMTP_SERVER, settings.SMTP_PORT) as server:
         server.starttls(context=context)
         server.login(settings.SMTP_USERNAME, settings.SMTP_PASSWORD)
-        server.send_message(msg, settings.SMTP_EMAIL, recipient)
+        try:
+            server.send_message(msg, settings.SMTP_EMAIL, recipient)
+        except smtplib.SMTPRecipientsRefused:
+            hyperion_error_logger.warning(
+                f'Bad email adress: "{", ".join(recipient)}" for mail with subject "{subject}".',
+            )