[NEW] add version 20.0 migration files

versions/20.0/pre_upgrade.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+set -euo pipefail
+
+echo "Prepare migration to 20.0..."
+
+# Copy database
+copy_database ou19 ou20 ou20 || exit 1
+
+
+# Execute SQL pre-migration commands
+PRE_MIGRATE_SQL=$(cat <<'EOF'
+EOF
+)
+echo "SQL command = $PRE_MIGRATE_SQL"
+query_postgres_container "$PRE_MIGRATE_SQL" ou20 || exit 1
+
+# Copy filestores
+copy_filestore ou19 ou19 ou20 ou20 || exit 1
+
+echo "Ready for migration to 20.0!"