test(e2e): add e2e tests

[shabaraba]

Why

This project needs end-to-end tests to verify the kintone Java client works correctly against a real kintone environment. Unit tests with mocks are valuable for testing internal logic, but they cannot catch issues with actual API integration, authentication flows, and real-world scenarios.

What

Added E2E Test Infrastructure

• GitHub Actions workflow (.github/workflows/e2e.yml):

  • Runs on push to master and manual dispatch
  • Supports specifying individual test classes
  • Includes proxy and authenticated proxy test jobs
  • Publishes JUnit test reports

• Test environment setup (e2e-tests/):

  • Gradle-based standalone test project
  • Environment variable configuration for kintone credentials
  • Docker-based proxy server for proxy tests
  • Helper scripts for running tests and updating client JAR

Known Limitations (Disabled Tests)

The following tests are @Disabled due to API or test environment constraints:

Test	Reason
AppApiTest.getStatistics()	Requires AppStatistics model update for new API fields
SpaceApiTest.getStatistics()	Requires SpaceStatistics model update for new API fields
AppPluginsTest.addPlugins()	Plugins cannot be deleted from app after adding
SpaceApiTest.deleteSpace()	Requires space recreation (not available with pre-created resources)
DeployTest.addApp()	Apps cannot be deleted after creation
DeployTest.deployApp_getDeployStatus()	Apps cannot be deleted after creation
DeployTest.deployApp_revert()	Apps cannot be deleted after creation

How to test

1. Set up environment variables (see e2e-tests/.env.example)
2. Create required test apps in kintone (see e2e-tests/README.md)
3. Run tests locally:

   cd e2e-tests
   ./bin/run-test.sh

4. Or run specific test class:

   ./bin/run-test.sh --tests SmokeTest

Checklist

• Read CONTRIBUTING.md at the repository.
• Updated documentation if it is required.
• Added/updated tests if it is required. (or tested manually)