oidc: add regression tests for token claim json

this helps to verify that the same JSON is produced,
after these types are refactored.

pkg/oidc/regression_create_test.go

@@ -0,0 +1,24 @@
+//go:build create_regression_data
+
+package oidc
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// Test_create_regression generates the regression data.
+// It is excluded from regular testing, unless
+// called with the create_regression_data tag:
+// go test -tags="create_regression_data" ./pkg/oidc
+func Test_create_regression(t *testing.T) {
+	for _, obj := range regressionData {
+		file, err := os.Create(jsonFilename(obj))
+		require.NoError(t, err)
+		defer file.Close()
+
+		encodeJSON(t, file, obj)
+	}
+}