Allow trac to notify yet-to-be-known OSGeo users

[strk]

As of Trac-1.2 upgrade (#1816) notifications are only possible toward users who are *known* by the specific trac instance. To be known, a user must log in at least once, ending in the trac "session" table as "authenticated".

This ticket is to evaluate whether to instead always lookup OSGeo usernames even if they never logged in, which is what we had before the upgrade (see #39).

Upstream discussion about this is here: ​https://trac.edgewall.org/ticket/12658#comment:31 A simple/short patch is available here: ​https://git.osgeo.org/gogs/strk/trac/commit/a72b9176f11b93629b4c96c93f131545d1b0e7b1

[strk]

See also #128 for other things a LDAP aware "RecipientMatcher" could do.

[strk]

I've just upgraded trac to current tip of the 1.2-stable branch (r15513) with the following patch applied:

commit 5b715da87632c56abfcc42379a99b4ddf7d5322f
Author: Sandro Santilli <strk@kbt.io>
Date:   Tue Jan 17 10:57:26 2017 +0100

    Allow resolving email of unknown users too (#12658)

diff --git a/trac/notification/mail.py b/trac/notification/mail.py
index 99cceec..e11f7f5 100644
--- a/trac/notification/mail.py
+++ b/trac/notification/mail.py
@@ -231,7 +231,7 @@ class RecipientMatcher(object):
                 address = "%s@%s" % (address, self.smtp_default_domain)
             else:
                 self.env.log.debug("Email address w/o domain: %s", address)
-                return None
+                return address, 0, None
 
         mo = self.shortaddr_re.search(address)
         if mo:

NOTE: at the time of writing, the patch above is committed in a fork of the Trac git repository hosted here: ​https://git.osgeo.org/gogs/strk/trac/src/t12658.strk