added oauth flow to get authorization code

pkg/oauth/config.go

@@ -0,0 +1,23 @@
+package oauth
+
+import (
+	"git.haelnorr.com/h/golib/env"
+	"github.com/pkg/errors"
+)
+
+type Config struct {
+	PrivateKey string // ENV OAUTH_PRIVATE_KEY: Private key for signing OAuth state tokens (required)
+}
+
+func ConfigFromEnv() (any, error) {
+	cfg := &Config{
+		PrivateKey: env.String("OAUTH_PRIVATE_KEY", ""),
+	}
+
+	// Check required fields
+	if cfg.PrivateKey == "" {
+		return nil, errors.New("Envar not set: OAUTH_PRIVATE_KEY")
+	}
+
+	return cfg, nil
+}