This patch adds checks that verify:
- The envelope from must match the authenticated user. This prevents
impersonation at the envelope level (while still allowing bounces, of
course).
- If the destination is remote, then the user must have completed
authentication. This prevents unauthorized relaying.
The patch ends up adjusting quite a few tests, as they were not written
considering these restrictions so they have to be changed accordingly.
This patch introduces a new directory, test/, which contains a simple local
end-to-end test which runs a chasquid binary and uses msmtp to send an email,
which is delivered locally.
As it's the first one, it adds a bunch of common infrastructure to simplify
writing these kinds of tests.
More end-to-end tests will follow, and it's expected that the common
infrastructure will also change significantly to accomodate their needs.
