refactor(logging): move logging setup to internal/logging

Moves logging configuration and setup to a dedicated package. Updates Config struct to use nested LoggingConfig. Updates main.go to use the new logging package.

internal/logging/logging.go

@@ -0,0 +1,37 @@
+package logging
+
+import (
+	"log/slog"
+	"os"
+	"strings"
+)
+
+// Config holds the logging configuration.
+type Config struct {
+	Level string `yaml:"level"`
+}
+
+// Configure sets up the global logger based on the provided configuration.
+func Configure(cfg Config) *slog.Logger {
+	opts := &slog.HandlerOptions{
+		Level: parseLogLevel(cfg.Level),
+	}
+	logger := slog.New(slog.NewJSONHandler(os.Stdout, opts))
+	slog.SetDefault(logger)
+	return logger
+}
+
+func parseLogLevel(level string) slog.Level {
+	switch strings.ToLower(level) {
+	case "debug":
+		return slog.LevelDebug
+	case "info":
+		return slog.LevelInfo
+	case "warn":
+		return slog.LevelWarn
+	case "error":
+		return slog.LevelError
+	default:
+		return slog.LevelInfo
+	}
+}

internal/logging/logging_test.go

@@ -0,0 +1,37 @@
+package logging
+
+import (
+	"log/slog"
+	"testing"
+)
+
+func TestParseLogLevel(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected slog.Level
+	}{
+		{"debug", slog.LevelDebug},
+		{"DEBUG", slog.LevelDebug},
+		{"info", slog.LevelInfo},
+		{"warn", slog.LevelWarn},
+		{"error", slog.LevelError},
+		{"unknown", slog.LevelInfo},
+		{"", slog.LevelInfo},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.input, func(t *testing.T) {
+			if got := parseLogLevel(tt.input); got != tt.expected {
+				t.Errorf("parseLogLevel(%q) = %v, want %v", tt.input, got, tt.expected)
+			}
+		})
+	}
+}
+
+func TestConfigure(t *testing.T) {
+	cfg := Config{Level: "debug"}
+	logger := Configure(cfg)
+	if logger == nil {
+		t.Error("Configure() returned nil")
+	}
+}