Thank you for being here! Currently do not provide an overall review approval status for a Pull Request. WE do have an open feature request for this and I'll add your use case to the issue.
However, The list reviews on a pull request endpoint will show you all of the reviews on a pull request with the standard 5000 requests per hour limit. Looping through the output looking for
"state": "APPROVED" will show whether the pull request was approved or not. Perhaps that could help?
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