Pass each subsystem a different Logger with its own group name so that
potential duplicates are qualified:

	logger := slog.Default().With("id", systemID)
	parserLogger := logger.WithGroup("parser")
	parseInput(input, parserLogger)

When parseInput logs with parserLogger, its keys will be qualified with "parser",
so even if it uses the common key "id", the log line will have distinct keys.

# Contexts