unsubscribe: get off mah lawn^H^H^Hist

While public-inbox is intended primarily for archival,
SMTP list subscriptions are still in use in most places
and users are likely to want a good unsubscribe mechanism.

HTTP (or HTTPS) links in the List-Unsubscribe header are
often preferable since some users may use an incorrect
email address for mailto: links.

Thus, it is useful to provide an example which generates an
HTTPS link for users to click on.  The default .psgi requires
a POST confirmation (as destructive actions with GET are
considered bad practice).  However, the "confirm" parameter
may be disabled for a true "one-click" unsubscribe.

The generated URLs are hopefully short enough and both shell
and highlighting-friendly to reduce copy+paste errors.

1 files changed, 24 insertions, 0 deletions

diff --git a/examples/unsubscribe-milter@.service b/examples/unsubscribe-milter@.service
new file mode 100644
index 00000000..98e3d478
--- /dev/null
+++ b/examples/unsubscribe-milter@.service
@@ -0,0 +1,24 @@
+# ==> /etc/systemd/system/unsubscribe-milter@.service <==
+# The '@' is to allow multiple simultaneous services to start
+# and share the same socket so new code can be cycled in
+# without downtime
+
+[Unit]
+Description = unsubscribe milter %i
+Wants = unsubscribe-milter.socket
+After = unsubscribe-milter.socket
+
+[Service]
+# First 8 bytes is for the key, next 8 bytes is for the IV
+# using Blowfish.  We want as short URLs as possible to avoid
+# copy+paste errors
+# umask 077 && dd if=/dev/urandom bs=16 count=1 of=.unsubscribe.key
+ExecStart = /usr/local/sbin/unsubscribe.milter /home/mlmmj/.unsubscribe.key
+Sockets = unsubscribe-milter.socket
+
+# the corresponding PSGI app needs permissions to modify the
+# mlmmj spool, so we might as well use the same user since
+User = mlmmj
+
+[Install]
+WantedBy = multi-user.target