the service api of HITL

[hjlarry]

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1. Is this request related to a challenge you're experiencing? Tell me about your story.

after the HITL added in 1.13, if a workflow or chatflow contains HITL, you can't request it via service API. we should add the service API of HITL

it also affect some related projects can't use, lexmin0412/dify-chat#443

2. Additional context or comments

No response

3. Can you help us with this feature?

• I am interested in contributing to this feature.

[dosubot]

I updated an issue I reported earlier to be in first person singular.

[github-actions]

Closed due to inactivity. If you have any questions, you can reopen it.