Fix flaky postgres test (#7228)

* Fix flaky postgres test

* add pgcrypto extension to test

* fix postgres ref link CONTRIBUTING guide and add pgcrypto extension

* Update CONTRIBUTING.md

scripts/before_script_postgres.sh

@@ -7,6 +7,7 @@ echo "[SCRIPT] Before Script :: Setup Parse DB for Postgres"
 PGPASSWORD=postgres psql -v ON_ERROR_STOP=1 -h localhost -U postgres <<-EOSQL
     CREATE DATABASE parse_server_postgres_adapter_test_database;
     \c parse_server_postgres_adapter_test_database;
+    CREATE EXTENSION pgcrypto;
     CREATE EXTENSION postgis;
     CREATE EXTENSION postgis_topology;
 EOSQL