curl --request POST \
  --url https://api.example.com/api/v1/campaigns/{campaign_id}/leads/{campaign_lead_id}/unapprove \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "step_index": 16
}
'

{
  "campaign_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "campaign_lead_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "updated_at": "2023-11-07T05:31:56Z",
  "step_index": 123,
  "approved_steps": [
    123
  ],
  "approved_entry": {
    "subject": "<string>",
    "body": "<string>",
    "prompt_snapshot": "<string>",
    "prompt_version_hash": "<string>",
    "lead_identity_fingerprint": "<string>",
    "step_index": 123,
    "variant_label": "<string>",
    "step_config_fingerprint": "<string>",
    "approved_at": "2023-11-07T05:31:56Z",
    "approved_by": "<string>",
    "research_cache_fingerprint": "<string>",
    "sender_profile_id": "<string>",
    "template_id": "<string>",
    "model": "<string>",
    "generation_latency_ms": 123
  }
}