invoices: also run amount-validator on setter

- @amount_msat.validator prevents the creation of invoices with e.g. too large amounts
- however the qml gui is mutating invoices by directly setting the `amount_msat` field,
  and it looks like attrs validators only run during init.
  We can use `on_setattr` (introduced in attrs==20.1.0).
- a wallet db upgrade is added to rm existing insane invoices
- btw the qml gui was already doing its own input validation on the textedit
  (see qeconfig.btcAmountRegex). however that only limits the input to not have more
  chars than what is needed to represent 21M BTC (e.g. you can still enter 99M BTC,
  which the invoice logic does not tolerate later on - but is normally caught).

fixes https://github.com/spesmilo/electrum/issues/8582

electrum/tests/test_invoices.py

@@ -5,10 +5,10 @@ from . import ElectrumTestCase
 
 from electrum.simple_config import SimpleConfig
 from electrum.wallet import restore_wallet_from_text, Standard_Wallet, Abstract_Wallet
-from electrum.invoices import PR_UNPAID, PR_PAID, PR_UNCONFIRMED, BaseInvoice
+from electrum.invoices import PR_UNPAID, PR_PAID, PR_UNCONFIRMED, BaseInvoice, Invoice, LN_EXPIRY_NEVER
 from electrum.address_synchronizer import TX_HEIGHT_UNCONFIRMED
 from electrum.transaction import Transaction, PartialTxOutput
-from electrum.util import TxMinedInfo
+from electrum.util import TxMinedInfo, InvoiceError
 
 
 class TestWalletPaymentRequests(ElectrumTestCase):
@@ -266,3 +266,39 @@ class TestWalletPaymentRequests(ElectrumTestCase):
         BaseInvoice._get_cur_time = lambda *args: time.time() + 200_000
         self.assertEqual(PR_UNCONFIRMED, wallet1.get_invoice_status(pr2))
         self.assertEqual(pr2, wallet1.get_request_by_addr(addr1))
+
+
+class TestBaseInvoice(ElectrumTestCase):
+    TESTNET = True
+
+    async def test_arg_validation(self):
+        amount_sat = 10_000
+        outputs = [PartialTxOutput.from_address_and_value("tb1qmjzmg8nd4z56ar4fpngzsr6euktrhnjg9td385", amount_sat)]
+        invoice = Invoice(
+            amount_msat=amount_sat * 1000,
+            message="mymsg",
+            time=1692716965,
+            exp=LN_EXPIRY_NEVER,
+            outputs=outputs,
+            bip70=None,
+            height=0,
+            lightning_invoice=None,
+        )
+        with self.assertRaises(InvoiceError):
+            invoice.amount_msat = 10**20
+        with self.assertRaises(InvoiceError):
+            invoice2 = Invoice(
+                amount_msat=10**20,
+                message="mymsg",
+                time=1692716965,
+                exp=LN_EXPIRY_NEVER,
+                outputs=outputs,
+                bip70=None,
+                height=0,
+                lightning_invoice=None,
+            )
+        with self.assertRaises(TypeError):
+            invoice.time = "asd"
+        with self.assertRaises(TypeError):
+            invoice.exp = "asd"
+