In the next commit, we'll bump our lnd dependency to `v0.18.3-beta`.
That version adds explicitly declared optional protos fields with commit
3de6c5415a
Optional proto fields are only available in Proto3 after protoc version
`3.15+`, and we therefore need to bump our protoc version for the protos
generation script to support them.
When doing so, we mimic the protobuf-compiler version used in `lnd`,
which is `3.21.12`. As protobuf-compiler 3.21.x+ is only available for
Node.js base images with Debian 12 (bookworm), we also update our NodeJS
base image to version 22.8.0-bookworm.