Claude-assisted improvements (untested)

- dev auth flow (side-step OAuth)
- db event processing integration tests
- dev scripts (eg Makefile)
- db / test db migration setup scripts.

config/config.go

@@ -0,0 +1,76 @@
+// Package config loads application configuration from environment variables,
+// optionally populated from a .env file in the working directory.
+package config
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+
+	"github.com/joho/godotenv"
+)
+
+type Config struct {
+	DatabaseURL string
+
+	Auth0Domain       string
+	Auth0ClientID     string
+	Auth0ClientSecret string
+	Auth0CallbackURL  string
+
+	EtsyAPIKeystring    string
+	EtsyAPISharedSecret string
+
+	// DevAuthEnabled, when true, exposes a route that mints a local
+	// login session for any user_id without going through Auth0. Must
+	// never be true outside local development.
+	DevAuthEnabled bool
+}
+
+// Load reads a .env file, if present, into the process environment, then
+// reads the required configuration values from the environment.
+func Load() (Config, error) {
+	if err := godotenv.Load(); err != nil && !os.IsNotExist(err) {
+		return Config{}, fmt.Errorf("failed to load .env file: %w", err)
+	}
+
+	var (
+		cfg     Config
+		missing []string
+	)
+
+	required := func(key string) string {
+		v := os.Getenv(key)
+		if v == "" {
+			missing = append(missing, key)
+		}
+		return v
+	}
+
+	cfg.DatabaseURL = required("DATABASE_URL")
+
+	cfg.Auth0Domain = required("AUTH0_DOMAIN")
+	cfg.Auth0ClientID = required("AUTH0_CLIENT_ID")
+	cfg.Auth0ClientSecret = required("AUTH0_CLIENT_SECRET")
+	cfg.Auth0CallbackURL = required("AUTH0_CALLBACK_URL")
+
+	cfg.EtsyAPIKeystring = required("ETSY_API_KEYSTRING")
+	cfg.EtsyAPISharedSecret = required("ETSY_API_SHARED_SECRET")
+
+	if len(missing) > 0 {
+		return Config{}, fmt.Errorf(
+			"missing required environment variables: %v (see .env.example)",
+			missing,
+		)
+	}
+
+	if raw := os.Getenv("DEV_AUTH_ENABLED"); raw != "" {
+		devAuthEnabled, err := strconv.ParseBool(raw)
+		if err != nil {
+			return Config{}, fmt.Errorf("invalid DEV_AUTH_ENABLED value %q: %w", raw, err)
+		}
+		cfg.DevAuthEnabled = devAuthEnabled
+	}
+
+	return cfg, nil
+}