E-Mail: Automatically set 'allow_self_signed=true' for 'mail_smtphost = localhost'

[Cybso]

The newer versions of Nextcloud use StartTLS per default, resulting in many bug reports when used with self-signed certificates:

#37329
#37694
#38957
#39452
#39538
#40073

There is a workaround to allow self signed certificates by manually editing config.php:

  "mail_smtpstreamoptions" => array(
    'ssl' => array(
        'allow_self_signed' => true,
        'verify_peer' => false,
        'verify_peer_name' => false
    )   
  ),  

But since many users will stumble across this problem let me suggest a small change:

If "mail_smtphost" is set to "localhost" or "127.0.0.1" and the above parameters are not explicitly configured, then assume that the user wants to accept unverified self-signed certificates by default - or do not use StartTLS at all for local connections.

[Cybso]

I have written a short POC patch, works perfectly for me:

nextcloud-41935-poc.patch.txt