LearnDash Quiz to Sheets Snippet

I need a small WordPress snippet that hooks into LearnDash and, immediately after each quiz submission, grabs the results in JSON format along with full user-specific details which user input their info on a page, the quiz is also add to that page by shortcode. The code should then push that data straight to a connected Google Sheet.

Scope is intentionally lean: a single, well-commented PHP function file that
• listens for the quiz-completed action in LearnDash,
• bundles the quiz score, percentages, and the user’s details into JSON,
• authenticates once with Google Sheets (API v4 or Apps Script webhook is fine) and appends the new row.

No interface, settings page, or historical backfill is needed—just the working hook and clear setup notes so I can copy and paste it into a snippet code.