Handle various Stripe.js error responses

# Problem

This issue can serve as a compiled list of `Stripe.js` error responses we can encounter. Typically, these occur when we're creating tokens, for example, for cards, bank accounts, etc.

We may want to use them in the future, to generate validation errors for components of our account setup form.

List of error responses:

```JSON
{
"error": {
"type": "invalid_request_error",
"message": "Routing number must have 9 digits",
"param": "bank_account"
}
}

// we can probably punt this one

{
"error": {
"type": "invalid_request_error",
"message": "You cannot use a live bank account number when making transfers or debits in test mode",
"param": "bank_account"
}
}
```

該 issue 提到了 Stripe.js token 的建立和帳戶設定表單，但沒有指出檔案、測試或進入點。首先定位 Stripe.js token 的建立流程及其表單驗證，然後釐清列出的哪些回應需要處理；只有在就這些回應的行為達成共識並具備相應的驗證涵蓋範圍後，才算完成。

由索引模型根據 Issue 內容生成。