Decoding a malformed or wrong-network invoice (e.g. a regtest lnbcrt...
invoice on a mainnet node) made each backend fail with a cryptic,
leaked error: LND with the Go 'strconv.ParseUint: parsing "rt500":
invalid syntax' surfaced as a 500, and CLN with 'Invalid bolt11: ...'.
Add a shared helper raise_for_pay_req_decode_error() in lightning/utils
that recognizes the decode-failure signatures of both backends and
raises one clear 400 pointing at the likely cause (malformed or wrong
network). Wire LND (lnd_grpc), CLN gRPC and CLN JSON-RPC through it so
they behave identically; genuine backend errors still return 500.
Fixes#225
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Implementations sometimes don't find aliases in the gossip, even if
they are openeing a channel to the pubkey. In this case an empty
string will be returned and the problem logged in debug mode.
refs #199
