logging: suppress log entries that are not structured

Borrowed from the BC4 configuration.

config/environments/production.rb

@@ -50,6 +50,10 @@ Rails.application.configure do
                                        .tap  { |logger| logger.formatter = ::Logger::Formatter.new }
                                        .then { |logger| ActiveSupport::TaggedLogging.new(logger) }
 
+  # No normal logs. Suppress everything that's not structured.
+  config.logger = ActiveSupport::TaggedLogging.new(ActiveSupport::Logger.new(nil))
+  config.log_level = :fatal
+
   # Structured JSON logging
   config.structured_logging.logger = ActiveSupport::Logger.new(STDOUT)