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/core/tools/errors.py

@@ -1,4 +1,5 @@
 from core.tools.entities.tool_entities import ToolInvokeMeta
+from libs.exception import BaseHTTPException
 
 
 class ToolProviderNotFoundError(ValueError):
@@ -37,6 +38,12 @@ class ToolCredentialPolicyViolationError(ValueError):
     pass
 
 
+class WorkflowToolHumanInputNotSupportedError(BaseHTTPException):
+    error_code = "workflow_tool_human_input_not_supported"
+    description = "Workflow with Human Input nodes cannot be published as a workflow tool."
+    code = 400
+
+
 class ToolEngineInvokeError(Exception):
     meta: ToolInvokeMeta