feat(api): Human Input Node (backend part) (#31646)

The backend part of the human in the loop (HITL) feature and relevant architecture / workflow engine changes.

Signed-off-by: yihong0618 <zouzou0208@gmail.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: -LAN- <laipz8200@outlook.com>
Co-authored-by: 盐粒 Yanli <yanli@dify.ai>
Co-authored-by: CrabSAMA <40541269+CrabSAMA@users.noreply.github.com>
Co-authored-by: Stephen Zhou <38493346+hyoban@users.noreply.github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: yihong <zouzou0208@gmail.com>
Co-authored-by: Joel <iamjoel007@gmail.com>

api/tests/unit_tests/controllers/service_api/app/test_workflow_fields.py

@@ -0,0 +1,25 @@
+from types import SimpleNamespace
+
+from controllers.service_api.app.workflow import WorkflowRunOutputsField, WorkflowRunStatusField
+from core.workflow.enums import WorkflowExecutionStatus
+
+
+def test_workflow_run_status_field_with_enum() -> None:
+    field = WorkflowRunStatusField()
+    obj = SimpleNamespace(status=WorkflowExecutionStatus.PAUSED)
+
+    assert field.output("status", obj) == "paused"
+
+
+def test_workflow_run_outputs_field_paused_returns_empty() -> None:
+    field = WorkflowRunOutputsField()
+    obj = SimpleNamespace(status=WorkflowExecutionStatus.PAUSED, outputs_dict={"foo": "bar"})
+
+    assert field.output("outputs", obj) == {}
+
+
+def test_workflow_run_outputs_field_running_returns_outputs() -> None:
+    field = WorkflowRunOutputsField()
+    obj = SimpleNamespace(status=WorkflowExecutionStatus.RUNNING, outputs_dict={"foo": "bar"})
+
+    assert field.output("outputs", obj) == {"foo": "bar"}