Incorporate original subject in autoresponder

[ChristophWurst]

Is your feature request related to a problem? Please describe.

As a user I set an autoresponder for vacation, sickness or other absence. To give the recipient of an automatically generated response context about the message, I would like the email to contain the original subject.

Describe the solution you'd like

When I set my responder subject to Out of office someone contacts me with subject Oversize pulley wheels are a scam, then the autoresponder should be Out of office, RE: Oversize pulley wheels are a scam.

If I read https://dovecot.org/pipermail/dovecot/2008-July/032237.html correctly this should be possible with Sieve.

Describe alternatives you've considered

N/a

Additional context

cc @st3iny