API documentation updates

Hello ,

I discovered for wix-billing-backend API that the documentation doesn't correspond at all with the event I got on the live site

This is just a small example event from API reference

{
	"id": {
		"id": "411a5551-b0f6-4826-8a41-ebae2879f857",
		"version": 25
	},
	"status": "Draft",
	"number": "0000003",
	"title": "My Invoice",
	"currency": "USD",
	"customer": {
		"contactId": "4f7c6637-0657-4696-a00b-9bc2ae4e035d",
		"email": "john.doe@somedomain",
		//MORE LINES...
	}
}

compared with the actual event

{
	"id": {
		"id": "5ead9806-03d6-40bd-8c64-10207f072a12",
		"version": 33
	},
	"data": {
		"number": "0000005",
		"currencyCode": "EUR",
		"customer": {
			"contactId": "6fe427c6-d2ba-41a7-b66c-ceb5652ecb0f",
			"name": "xxx@yahoo",
			"email": {
				"address": "xxxx@yahoo"
			}
			//MORE LINES...
		}
		
//MORE LINES...
	}
}

Can I see somewhere the actual version of the API ?

How should I treat following updates ? Will the API at least remain the same for the live site? or I can expect it to change on one day and my code to stop working...