App Script that receives webhook requests and records them in a Google Spreadsheet.

webhook_recorder.gs

function doPost(e) {
  const sheet = SpreadsheetApp.getActiveSpreadsheet().getSheets()[0];

  sheet.getRange("1:1").insertCells(SpreadsheetApp.Dimension.ROWS);
  sheet.getRange(1, 1).setValue((new Date).toLocaleString('ja-JP'));
  sheet.getRange(1, 2).setValue(e.postData.contents);

  // send 200 OK status back to confirm receiving webhook
  var response = HtmlService.createHtmlOutput();
  return response;
}