Define the configuration section in a better place than leaf-config-reading-functions
From https://github.com/PrivateStorageio/ZKAPAuthorizer/pull/255#discussion_r762180297:
This feels like a weird place for this constant. I'd prefer if this were passed in from _plugin. (If we had infinite time, I'd likely suggest having an object wrapping the node config, that reads from a particular section, but it probably isn't worth the effort here yet).