[API] Properly handle non-BigInt authorID's

[spifory]

There should be some proper error handling for this. I initially did it like this because I was lazy, and once again to get the actual bot and API working.

The way it currently does it works, but it's quite hard to understand. It should at least specify that it needs a BigInt and not a random string instead of doing what it currently does.

tags/api/src/previews/previewService.ts

Lines 12 to 15 in 7bc95ab

	// it will error when a BigInt is not a BigInt and then turn it into a string again
	// just so that it can go in to the database correctly
	// I have no idea why I'm doing it like this
	authorID: String(BigInt(data.authorID)),