feat: oidc client data preview (#624)

Co-authored-by: Elias Schneider <login@eliasschneider.com>

backend/internal/utils/jwt_util.go

@@ -0,0 +1,19 @@
+package utils
+
+import (
+	"fmt"
+
+	"github.com/lestrrat-go/jwx/v3/jwt"
+)
+
+func GetClaimsFromToken(token jwt.Token) (map[string]any, error) {
+	claims := make(map[string]any)
+	for _, key := range token.Keys() {
+		var value any
+		if err := token.Get(key, &value); err != nil {
+			return nil, fmt.Errorf("failed to get claim %s: %w", key, err)
+		}
+		claims[key] = value
+	}
+	return claims, nil
+}