fix: relative path destination local mode

[NicoleMGomes]

Description

LocalDevClientBase.__init__ and the _mock_file() helper in destination/__init__.py resolved the mocks/ directory by navigating three levels up from __file__:

repo_root = os.path.abspath(
    os.path.join(os.path.dirname(__file__), "..", "..", "..")
)

This works in a source checkout (src/sap_cloud_sdk/destination/ → three levels up → project root), but when the package is installed into a virtual environment it lands at .venv/lib/python3.x/site-packages/sap_cloud_sdk/destination/, making three levels up resolve to .venv/lib/python3.x/ instead of the project root. As a result get_instance_destination() silently returns None.

Both locations now use os.getcwd(), which always resolves to the directory the application is launched from, regardless of install location:

self._file_path = os.path.join(os.getcwd(), "mocks", self.file_name)

Unit test fixtures that previously patched os.path.abspath were updated to patch os.getcwd instead.

Related Issue

Closes #46

Type of Change

Please check the relevant option:

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Code refactoring
• Dependency update

How to Test

1. Create a project that uses sap_cloud_sdk installed from a virtual environment (not a source checkout).
2. Add mocks/destination.json at the project root with at least one destination entry.
3. Run:

   from sap_cloud_sdk.destination import create_client
   client = create_client(instance="destination-service")
   print(client._file_path)   # should print <project-root>/mocks/destination.json
   dest = client.get_instance_destination("my-destination")
   print(dest)                # should print the destination object, not None

4. Confirm _file_path points to the project root and get_instance_destination() returns the expected destination.

Alternatively, run the unit test suite:

uv run pytest tests/destination/unit/ -v

Checklist

Before submitting your PR, please review and check the following:

• I have read the Contributing Guidelines
• I have verified that my changes solve the issue
• I have added/updated automated tests to cover my changes
• All tests pass locally
• I have verified that my code follows the Code Guidelines
• I have updated documentation (if applicable)
• I have added type hints for all public APIs
• My code does not contain sensitive information (credentials, tokens, etc.)
• I have followed Conventional Commits for commit messages

Breaking Changes

None. The fix only affects the path resolution for local development mock files. Any project that already placed mocks/destination.json at the project root and ran the application from that root will see identical behaviour.

Additional Notes

The same __file__-based pattern was present in two places — _local_client_base.py and the _mock_file() helper in destination/__init__.py — both are fixed.

[ArthurTonial]