feat: return variable value if it is a generic variable (#5366)

* fix: update pre-commit configuration for ruff formatting args

* fix: update variable type constant from GENERIC_TYPE to CREDENTIAL_TYPE

* feat: enhance variable service to handle decryption for generic type and update default variable type to CREDENTIAL_TYPE

* feat: add abstract method to retrieve all variables for a user in VariableService

* feat: implement get_all method in KubernetesSecretService to retrieve and decrypt user variables

* refactor: update variable tests to use fixtures for generic and credential types

- Renamed and refactored test fixtures for better clarity and reusability.
- Updated tests to utilize `generic_variable` and `credential_variable` fixtures instead of hardcoded values.
- Enhanced assertions to ensure correct handling of variable types, including encryption for credential variables and decryption for generic variables.
- Improved test structure for creating, reading, updating, and deleting variables, ensuring consistency across test cases.

* refactor: update get_all method signatures in variable services to return VariableRead

- Changed return type of the get_all method in VariableService, KubernetesSecretService, and DatabaseVariableService from list[Variable | None] to list[VariableRead].
- This update enhances type consistency across variable services and aligns with the new VariableRead model for improved data handling.

* fix: update variable type assertion in test_update_variable to CREDENTIAL_TYPE

- Changed the assertion in the `test_update_variable` test to verify that the result type is now `CREDENTIAL_TYPE` instead of `GENERIC_TYPE`.
- This update aligns the test with recent changes in variable type handling, ensuring accurate validation of variable updates.

* fix: update variable type assertion in test_create_variable to CREDENTIAL_TYPE

- Changed the assertion in the `test_create_variable` test to verify that the result type is now `CREDENTIAL_TYPE` instead of `GENERIC_TYPE`.
- This update ensures consistency with recent changes in variable type handling and improves the accuracy of the test validation.

src/backend/tests/unit/services/variable/test_service.py

@@ -6,7 +6,7 @@ import pytest
 from langflow.services.database.models.variable.model import VariableUpdate
 from langflow.services.deps import get_settings_service
 from langflow.services.settings.constants import VARIABLES_TO_GET_FROM_ENVIRONMENT
-from langflow.services.variable.constants import CREDENTIAL_TYPE, GENERIC_TYPE
+from langflow.services.variable.constants import CREDENTIAL_TYPE
 from langflow.services.variable.service import DatabaseVariableService
 from sqlalchemy.ext.asyncio import create_async_engine
 from sqlmodel import SQLModel
@@ -137,7 +137,7 @@ async def test_update_variable(service, session: AsyncSession):
     assert result.value != old_value
     assert result.value != new_value
     assert result.default_fields == []
-    assert result.type == GENERIC_TYPE
+    assert result.type == CREDENTIAL_TYPE
     assert isinstance(result.created_at, datetime)
     assert isinstance(result.updated_at, datetime)
 
@@ -237,6 +237,6 @@ async def test_create_variable(service, session: AsyncSession):
     assert result.name == name
     assert result.value != value
     assert result.default_fields == []
-    assert result.type == GENERIC_TYPE
+    assert result.type == CREDENTIAL_TYPE
     assert isinstance(result.created_at, datetime)
     assert isinstance(result.updated_at, datetime)