Allow From to be set on notifications (SMS and email)

[elvey]

The notify command is documented at https://www.fastmail.fm/docs/sieve/fm-sieve-notify.html

I propose an additional option pair,

"Source", "<source>" Defines the source of the message

<source> Can be either a phone number or an email address (depending on the value of <method>)

Currently, source is always the user's default Personality.


I can see that adding this feature might be an issue with SMS, as it's not supposed to be easy to forge SMS messages, but at when it comes to mailto, this should be a non-issue.