Business, now more than ever before, is going digital, and today a startup that’s building a vertically integrated solution to meet business banking needs is announcing a big round of funding to tap into the opportunity. Airwallex — which provides business banking services both directly to businesses themselves, as well as via a set of APIs that power other companies’ fintech products — has raised $200 million, a Series E round of funding that values the Australian startup at $4 billion. Lone Pine Capital is leading the round, with new…