## Description
PR to add the check for `appsmith` user existence before any assertions
in pg-auth-test to remove the flakiness.
### 🔍 Cypress test results
<!-- This is an auto-generated comment: Cypress test results -->
> [!WARNING]
> Tests have not run on the HEAD
0ac8736872f1d8b51b384b644dd0f3b21f725cb0 yet
> <hr>Fri, 13 Dec 2024 05:18:03 UTC
<!-- end of auto-generated comment: Cypress test results -->
## Communication
Should the DevRel and Marketing teams inform users about this change?
- [ ] Yes
- [x] No
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
- **Bug Fixes**
- Enhanced testing for PostgreSQL authentication to ensure the Appsmith
user exists before access checks.
- **Tests**
- Updated existing test functions to include user existence
verification, improving the robustness of the testing process.
- Introduced new functions to verify user existence and check the
readiness of the Appsmith instance and PostgreSQL.
- Streamlined logic for readiness checks, enhancing overall testing
efficiency.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
