Gateway security release
This release fixes a bug in the Lightning gateway's LNv1 payment handling and adds further hardening to the gateway's payment paths, including the LNv2 module and the LND and LDK backends.
Gateway operators should upgrade as soon as possible. Details are being withheld for now to give operators time to update.
This is a drop-in upgrade: no protocol, consensus, API or database format changes. Federation guardians and wallet users are not affected and need not take action. The same changes ship in v0.12.1 for gateways on the 0.12 line; operators on 0.10 or older should move to a supported release.
