EC-76387: [Alternative] Fix ESM compatibility with simpler mocking approach (#1215)

* Bump @actions/core from 2.0.3 to 3.0.0

Bumps [@actions/core](https://github.com/actions/toolkit/tree/HEAD/packages/core) from 2.0.3 to 3.0.0.
- [Changelog](https://github.com/actions/toolkit/blob/main/packages/core/RELEASES.md)
- [Commits](https://github.com/actions/toolkit/commits/HEAD/packages/core)

---
updated-dependencies:
- dependency-name: "@actions/core"
  dependency-version: 3.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

* EC-76387: Fix ESM compatibility with simpler mocking approach

The @actions/core v3.0.0 upgrade introduces ESM-only modules which breaks Jest tests.

This PR uses a simpler approach than jest.unstable_mockModule:
- Creates simple fake objects instead of module-level mocking
- Uses helper functions for cleaner, more readable tests
- Still requires Jest ESM configuration changes

Changes:
- Updated Jest config to support ESM modules
- Added --experimental-vm-modules flag to npm test script
- Refactored eventService.test.ts to use simple fake objects

Co-Authored-By: Mikkel Sander Guntveit <mikkel.guntveit@visma.com>

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: ecoai-bot <ecoai-bot@e-conomic.com>
Co-authored-by: Mikkel Sander Guntveit <mikkel.guntveit@visma.com>

Author: 4 people

jest.config.js

@@ -2,7 +2,14 @@ module.exports = {
   preset: 'ts-jest',
   testEnvironment: 'node',
   transform: {
-    '^.+\\.js?$': 'babel-jest'
+    '^.+\\.tsx?$': ['ts-jest', {
+      useESM: true
+    }],
+    '^.+\\.jsx?$': 'babel-jest'
   },
-  transformIgnorePatterns: ['node_modules/(?!@library)/']
+  transformIgnorePatterns: ['node_modules/(?!@actions)/'],
+  extensionsToTreatAsEsm: ['.ts'],
+  moduleNameMapper: {
+    '^(\\.{1,2}/.*)\\.js$': '$1'
+  }
 }

package-lock.json

@@ -13,7 +13,7 @@
     "lint:fix": "npm run lint -- --fix",
     "package": "npm run clean:package && npm run build && npm run package:single",
     "package:single": "ncc build --out dist --minify --source-map --v8-cache",
-    "test": "jest",
+    "test": "NODE_OPTIONS='--experimental-vm-modules' jest",
     "test:ci": "npm run test -- --ci",
     "test:coverage": "npm run test -- --collect-coverage",
     "test:watch": "npm run test:coverage -- --watch --verbose false",
@@ -36,7 +36,7 @@
   },
   "homepage": "https://github.com/e-conomic/mergebot#readme",
   "dependencies": {
-    "@actions/core": "2.0.3",
+    "@actions/core": "3.0.0",
     "@actions/github": "9.0.0",
     "@octokit/auth-app": "7.1.4",
     "@octokit/rest": "21.1.0",