This can be useful in cases when:
1. outgoing-cred-cmd requires a user action or confirmation (e.g. when
using pass with a Yubikey or similar smart card that requires a user
to enter a pin or touch the device when decrypting the password)
2. A user starts aerc frequently, but not all the sessions end up with
sending emails
3. So the user only wants to execute outgoing-cred-cmd when the password
is really used, so the user doesn't have to enter pin or touch their
Yubikey each time aerc starts
Signed-off-by: Stas Rudakou <stas@garage22.net>
Acked-by: Robin Jarry <robin@jarry.cc>
ca90343850