Skip Loginview create when credentials already exist

[qcserestipy]

Fixes #267

Check for Existing Credentials and Bypass Login View Creation

1. Implemented a verification step to detect existing Harbor credentials in the current configuration.
2. If valid credentials are found, the creation of a new login view is skipped.
3. Enhances login efficiency by reusing stored credentials and reducing unnecessary prompts.

ToDo: Add base64 encoding for password in config file?

[qcserestipy]

To resolve the failing tests I will introduce a mock Keyring since the container has no keyring.