Allow the bulk and selective email restoration by smtp

[stephdl]

This pull request updates the environment variable names in the codebase to use "PROVIDER_IP" instead of "IMAP_HOST" for the IMAP host configuration. This change ensures consistency and clarity in the codebase because imap host === smtp host

Allow the auditor to restore by smtp on the IP of VPN without authentication (unencrypted on 25), we have no more imap authentication because we need to make an event during the domain creation/deletion in the mail server and also create a map action with email alias and username.

Note: you can select one email or the bulk restoration, everything is sent by smtp as an email, however the domain must be listed inside the piler UI

For restoration You have to set the email where to send the emails, the cons is that everything is sent to inbox, with IMAP recovering it seems that piler respects inbox and sent

jsuto/piler#29

refs: NethServer/dev#6895

[stephdl]

Maybe we could use a rate limit by hour https://github.com/jsuto/piler/blob/bf28ea314b127086a5275b121a1fdeb4466c1d3b/config.php.in#L191

[stephdl]

however the restore to mailbox try to restore by imap, obviously it does not work with auditor

[DavidePrincipi]

This seems a good improvement!

BTW, the event handler has to connect with the local Redis replica.