Charge SMS and WhatsApp API usage more frequently

## Problem

For messaging service like SMS/WhatsApp,
currently the metered usage is charged in the next invoice
This may incur a high unpaid messaging cost but failed to be paid at the end of the month.

## Appetite

2 weeks

## Solution

### Charge more frequently

- Everyday, Authgear will update the SMS/Whatsapp API usage to Stripe
- charge the outstanding amount if it is > USD 50

### Lower per day message limit

For SMS/Whatsapp API set a per day limit at:

- Soft limit: 500
- Hard limit: 1000

When the soft limit is met, an email alert is sent to the user,
They should reply to customer services to review the quota and raise the limit for the tenant.