release cookies
Reading https://hexdocs.pm/mix/Mix.Tasks.Release.html, it seems that our releases will contain an erlang cookie that should probably be unique per instance. It can be set at runtime with the RELEASE_COOKIE environment variable, but I wonder what the best place to set this is. Our systemd unit files?
@plataformatec the cookie is used to connect nodes to each other, right? Is it also used for rpc?