Lock accepted quotes/offers

[n1smithy]

What version of Invoice Ninja are you running? ie v4.5 / v5
v5

What environment are you running?
Docker

Have you searched existing issues/requests?
yes

Additional context
A quote/offer should not be editable (under the same quote-number) after the client/customer accepted it. At least there should be a pop-up if one tries to save an edited and already accepted offer.

So quotes should have the option to lock them after they were marked as accepted (or other triggers). Because after an editing only the edited quote is shown in the client-portal. A customer could be upset off if one accidentely change a quote.