Add migration to mark local communities as such (#3257)

migrations/2023-06-22-051755_fix_local_communities_marked_non_local/down.sql

@@ -0,0 +1,2 @@
+-- Add a no-op statement to prevent `diesel migration redo` errors
+SELECT 1;

migrations/2023-06-22-051755_fix_local_communities_marked_non_local/up.sql

@@ -0,0 +1,5 @@
+update community c
+set local=true
+from local_site ls
+  join site s on ls.site_id=s.id
+where c.instance_id=s.instance_id and not c.local;