Slightly better invoice email subject

wiaflos-server.conf

@@ -78,6 +78,9 @@ server = localhost
 # Email attachment template
 #email_template= invoices/invoice1.tt2
 
+# Email message subject prefix
+#email_subject_prefix=
+
 # Email body template
 #email_message_template=
 

wiaflos/server/core/Invoicing.pm

@@ -1346,13 +1346,17 @@ sub sendInvoice
 #			}
 #		}
 
+		# Build email subject
+		my $emailSubject = $config->{'invoicing'}{'email_subject_prefix'} // "";
+		$emailSubject .= "$invoiceTitle: $invoiceNumber";
+
 		# Create message
 		my $msg = MIME::Lite->new(
 				From		=> $config->{'invoicing'}{'email_from'},
 				To			=> $emailAddy,
 				Bcc			=> $config->{'invoicing'}{'email_bcc'},
 				'Reply-To'	=> $config->{'invoicing'}{'email_reply_to'},
-				Subject		=> "Invoice: ".$invoice->{'Number'},
+				Subject		=> $emailSubject,
 				Type		=> 'multipart/mixed'
 		);