Display the grace period state on the dashboard #8264

Goal. A paid customer over their plan limit knows whether it is costing them money.

We do not charge for the first billing month an organisation goes between 100% and 200% of its limit. Every month over after that is charged as overage. That first month is the grace period, the name used throughout the codebase and on the page.

So an organisation sitting at 118% is in one of two situations, and the page cannot currently tell them apart:

• covered, nothing to pay this month
• charged, at the overage rate

Where it appears

• the over-limit banner
• the line under the meter
• the existing quota warning, which today says "automated billing for the overages may apply" because it cannot tell either

Needs #8256, which returns whether the covered month has been used.

Done when an organisation at 118% is told whether it is being charged, and nothing on the page hedges.