[Dovecot] A variable for the unix user or home path would be useful in some cases

[interfaSys sàrl]

Hello,

In our hosting environment, we let users share mailboxes across all
their domains and think it's best if the shared mailbox listing (in a
file) stays in their unix home path. That would be:
/home/USER/imap/shared-mailboxes.db

Unfortunately, it seems there is no way to generate that path using a
variable. Something like this would be convenient:
acl_shared_dict = file:%v/imap/shared-mailboxes.db

Instead, we have to use something like this:
acl_shared_dict = file:~/../../../shared-mailboxes.db
which only works for virtual users.

Did somebody solve this another way?

Could we have the unix user or home path as a variable?
Or could we have a modifier giving us the path or the unix user based on
the unix UID?

Cheers,

Olivier