The engine’s logger is simply a debug tool, and the main reason for
creating it was to avoid adding noise to Rails’ default log. It should
make it easier to debug the engine loading process. It’s also quite
flexible in that you can set the logger to be the same as
RAILS_DEFAULT_LOGGER should you with.
You can create the logger anywhere you like (before you do, the logger
is actually set to be a dummy object that will accept any and all
method calls silently, so you could set it to be any object you like
in theory), but I’d suggest you create the logger in environment.rb
unless there’s a good reason not to.