Add 'site_shorname' to config for inter-site communication.

Rocksolid_Light/rslight/rslight.inc.php

@@ -14,6 +14,7 @@ return [
   'enable_all_networks' => '1',
   'server_auth_user' => 'localuser',
   'server_auth_pass' => '<local_password>',
+  'site_shortname' => '',
   'rslight_title' => 'New Rocksolid Light Install',
   'title_full' => 'rslight',
   'hide_email' => '1',

Rocksolid_Light/rslight/scripts/setuphelper.php

@@ -24,6 +24,7 @@ return [
 'server_auth_pass' => 'The password for the local server user',
 
 # Site configuration
+'site_shortname' => 'Must be unique from other rslight sites. Blank to disable',
 'rslight_title' => 'The tagline at the top of the web page',
 'title_full' => 'The site title in the client browser bar', 
 'hide_email' => 'Truncate email addresses in From header (1=true, blank=false)',