feat(integration): add SAP S/4HANA connector (v0.6-compatible)

[VasuBansal7576]

Description

Adds a SAP S/4HANA integration module and updates it for compatibility with the latest Hive v0.6 credential/runtime patterns.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Documentation update

Related Issues

Fixes #3182

Changes Made

• Added SAP S/4HANA integration package:
  • integrations/sap_s4hana/connector.py
  • integrations/sap_s4hana/credentials.py
  • integrations/sap_s4hana/__init__.py
  • integrations/sap_s4hana/README.md
  • integrations/sap_s4hana/test_connector.py
• Updated credential access to work with current Hive credential store APIs.
• Fixed test import/runtime behavior so tests run reliably from repo root.
• Improved error-path test to assert correct request exception handling.

Testing

Describe the tests you ran to verify your changes:

• Manual testing performed

Additional verification run for this PR:

• PYTHONPATH=. pytest -q integrations/sap_s4hana/test_connector.py (8 passed)
• python -m compileall integrations/sap_s4hana

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Screenshots (if applicable)

N/A (backend/integration change)