lnworker: enforce creation of PaymentInfo for b11

Enforce that the information used to create a bolt11 invoice using
`get_bolt11_invoice()` is similar to the related instance of PaymentInfo
by requiring a PaymentInfo as argument for `get_bolt11_invoice()`.
This way the invoice cannot differ from the created PaymentInfo.
This allows to use the information in PaymentInfo for validation of
incoming htlcs more reliably.

To cover all required information for the creation of a b11 invoice the
PaymentInfo class has to be extended with a expiry and
min_final_cltv_expiry. This requires a db upgrade.

electrum/lnutil.py

@@ -505,9 +505,10 @@ MIN_FUNDING_SAT = 200_000
 # the minimum cltv_expiry accepted for newly received HTLCs
 # note: when changing, consider Blockchain.is_tip_stale()
 MIN_FINAL_CLTV_DELTA_ACCEPTED = 144
-# set it a tiny bit higher for invoices as blocks could get mined
-# during forward path of payment
-MIN_FINAL_CLTV_DELTA_FOR_INVOICE = MIN_FINAL_CLTV_DELTA_ACCEPTED + 3
+
+# buffer added to min_final_cltv_delta of created bolt11 invoices to make verifying the cltv delta
+# of incoming payment htlcs reliable even if some blocks have been mined during forwarding
+MIN_FINAL_CLTV_DELTA_BUFFER_INVOICE = 3
 
 # the deadline for offered HTLCs:
 # the deadline after which the channel has to be failed and timed out on-chain