feat: Allow variables to be defined outside a Component (#4316)

* feat: Allow variables to be defined outside a Component

Fixes #4315

Modify `prepare_global_scope` function in `src/backend/base/langflow/utils/validate.py` to evaluate classes, functions, and variables defined outside the Component's class.

* **Function Changes:**
  - Add evaluation of external classes using `ast.ClassDef`.
  - Add evaluation of external functions using `ast.FunctionDef`.
  - Add evaluation of external variables using `ast.Assign`.

* **Unit Tests:**
  - Add tests in `src/backend/tests/unit/test_validate_code.py` to verify the evaluation of external classes, functions, and variables.
  - Include tests for multiple external classes and external variables and functions.

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For more details, open the [Copilot Workspace session](https://copilot-workspace.githubnext.com/langflow-ai/langflow/issues/4315?shareId=XXXX-XXXX-XXXX-XXXX).

* [autofix.ci] apply automated fixes

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

src/backend/base/langflow/utils/validate.py

@@ -227,6 +227,16 @@ def prepare_global_scope(code, module):
             except ModuleNotFoundError as e:
                 msg = f"Module {node.module} not found. Please install it and try again"
                 raise ModuleNotFoundError(msg) from e
+        elif isinstance(node, ast.ClassDef):
+            # Compile and execute the class definition to properly create the class
+            class_code = compile(ast.Module(body=[node], type_ignores=[]), "<string>", "exec")
+            exec(class_code, exec_globals)
+        elif isinstance(node, ast.FunctionDef):
+            function_code = compile(ast.Module(body=[node], type_ignores=[]), "<string>", "exec")
+            exec(function_code, exec_globals)
+        elif isinstance(node, ast.Assign):
+            assign_code = compile(ast.Module(body=[node], type_ignores=[]), "<string>", "exec")
+            exec(assign_code, exec_globals)
     return exec_globals