Verify email contact when receiving event notification

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We get people notifying us of events via the event notification form on the website. When that happens, we invariable either want to query the details with them or ask them to check what we've added in response to the event notification. We do that via email.

Sometimes people don't get that email because their mail provider is treating emails from admin@derbyartsandtheatre.org.uk as SPAM. It's time consuming then to try to get hold of them. To mitigate this we should:

1. Send an email from admin@derbyartsandtheatre.org.uk automatically when they submit the notification form.
2. Immediately show them a page saying that we've sent that email and asking them to check they've received it because that's the email address we will contact them from with queries. Instructions to check SPAM folder, etc.