Throw Exception if Authentication Doesn't Return Auth Token

[bobbyg603]

I'm not sure why but I think our backend might return a 2xx code for a client id/client secret authentication error with no token. We should check this case and fail fast.

bugsplat-js-api-client/src/common/client/oauth-client-credentials-api-client/oauth-client-credentials-api-client.ts

Lines 54 to 55 in c2125b1

	this._accessToken = loginResponse.access_token;
	this._tokenType = loginResponse.token_type;