Hey! if you want to use google calendars to setup meeting here's what you can do:
Make a account on google console enable api's calendar api, gmail api and cloud api, download the json file and create a test user.
also after downloading the json file. generate a token.json:
Use it in your backend make the post route logic of gmail and calendar and connect it to your vapi through webhook insode request tool.
i hove this will resolve your problem