Mostrod crashes if there is an error unwrapping a DM

[chebizarro]

Any sort of error when unwrapping a NIP44/59 gift-wrapped DM will cause the mostro daemon to crash. Eg

Error: NIP44: Json: invalid value: integer `-5138953035001`, expected u64 not found in payload

and

Error: NIP44: Json: malformed signature not found in payload

Were both fatal errors caused by a malformed date field in a gift wrapped event.

The main error that causes the crash is thrown here:

mostro/src/nip59.rs

Lines 79 to 82 in 8fd10f3

	let seal = match Event::from_json(seal) {
	Ok(seal) => seal,
	Err(e) => return Err(BuilderError::NIP44(nip44::Error::NotFound(e.to_string()))),
	};

Which doesn't seem to be handled by the calling function here:

mostro/src/app.rs

Line 71 in 8fd10f3

let event = unwrap_gift_wrap(&my_keys, &event)?;

Nostr events that are malformed are normally rejected by relays, but the contents of a Gift Wrapped DM can only be read by the recipient and therefore need to be treated with extra care when deserializing. A production server should be able to gracefully recover from this kind of error without crashing.