* feat(python): Add specific error classes for StorageInvocation
Replace generic `Exception` raises with `NotFoundError` when the key is missing,
and `StorageInvocationError` for other response errors. This improves error
handling at call sites by avoiding overly generic exceptions.
# Conflicts:
# python/dify_plugin/invocations/storage.py
* test(python): Add test cases for `StorageInvocation`
- Ensure `StorageInvocation` raises the correct exceptions when data is missing
or `_backwards_invoke` returns an invalid response.
- Verify that `StorageInvocation` correctly processes the result returned
by `_backwards_invoke`.
* chore(python): fix linter violations
* feat(python): Change the exception `StorageInvocation.exist` raised
* test(python): Add test cases for `StorageInvocation.exist`.
QuantumGhost