Add migration for online_sessions flag

Author: patch0

scripts/database/pg/migrations/027.do.add-online-sessions.sql

@@ -0,0 +1,9 @@
+DO $$
+    BEGIN
+        BEGIN
+            ALTER TABLE cd_dojos ADD COLUMN online_sessions smallint NOT NULL DEFAULT 0;
+        EXCEPTION
+            WHEN duplicate_column THEN RAISE NOTICE 'column online_sessions already exists in cd_dojos.';
+        END;
+    END;
+$$