Add Vault certificate rotation operator

internal/rotator/vault_test.go

@@ -0,0 +1,35 @@
+package rotator
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestVaultLogin(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(response http.ResponseWriter, request *http.Request) {
+		if request.URL.Path != "/v1/auth/kubernetes/login" {
+			http.NotFound(response, request)
+			return
+		}
+		var body map[string]string
+		if err := json.NewDecoder(request.Body).Decode(&body); err != nil {
+			t.Fatal(err)
+		}
+		if body["role"] != "role" || body["jwt"] != "jwt" {
+			t.Fatalf("unexpected login body: %#v", body)
+		}
+		_ = json.NewEncoder(response).Encode(map[string]any{"auth": map[string]string{"client_token": "token"}})
+	}))
+	defer server.Close()
+
+	token, err := (vaultClient{baseURL: server.URL, client: server.Client()}).login(context.Background(), "role", "jwt")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if token != "token" {
+		t.Fatalf("unexpected token: %s", token)
+	}
+}