Bug 17866: Change sender for serial claim notifications

Currently, the From field uses the emailaddress of the staff client member
from the user context. This is exceptional in Koha. And might very well be,
as in our case, the cause of fraud detection warnings.
We should use branch email address or fallback to KohaAdminEmailAddress,
as we do (almost) everywhere else.

Test plan:
Go to subscription detail in Koha.
Go to Claims.
Select a missing issue and click Send notification.
Verify the sender address in the generated notification. (Make sure that
you receive this mail.)

Signed-off-by: Grace McKenzie <grace.mcky@gmail.com>

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>

C4/Letters.pm

@@ -572,10 +572,11 @@ sub SendAlerts {
         $letter->{content} =~ s/<order>(.*?)<\/order>/$1/gxms;
 
         # ... then send mail
+        my $library = Koha::Libraries->find( $userenv->{branch} );
         my %mail = (
             To => join( ',', @email),
             Cc             => join( ',', @cc),
-            From           => $userenv->{emailaddress},
+            From           => $library->branchemail || C4::Context->preference('KohaAdminEmailAddress'),
             Subject        => Encode::encode( "UTF-8", "" . $letter->{title} ),
             Message => $letter->{'is_html'}
                             ? _wrap_html( Encode::encode( "UTF-8", $letter->{'content'} ),