Separate internal tests from API tests and add integration/e2e tests

[Copilot]

This PR addresses the test organization issues raised in #XX by separating internal unit tests from API tests and adding comprehensive integration tests to prevent regressions like the kubeconfig persistence bug (#28).

Changes Made

Test Separation

Previously, all tests were mixed together in the cmd/ package, making it difficult to distinguish between testing internal implementation details versus the public CLI API. This has been reorganized:

• Unit tests remain in their respective packages (cmd/, internal/aws/, internal/kubeconfig/) and focus on testing internal functions and implementation details
• API tests moved to new test/api/ package and focus on testing the complete CLI interface behavior including command execution, logging, and help functionality
• Integration tests added to new test/integration/ package for end-to-end testing

Integration/E2E Tests Added

The new integration tests provide comprehensive coverage of the CLI functionality:

// Tests the complete aws list workflow
func TestAWSListBasic(t *testing.T) { ... }

// Tests the complete aws update workflow  
func TestAWSUpdateBasic(t *testing.T) { ... }

// Specifically addresses issue #28 - kubeconfig persistence
func TestKubeconfigPersistence(t *testing.T) { ... }

These tests run the actual kdiscover binary and verify:

• Commands execute without crashing
• Kubeconfig files are properly handled and persisted (addressing kubeconfig is not persisted #28)
• Error handling works correctly when AWS credentials are unavailable
• Help commands function properly
• Commands complete within reasonable timeouts

Benefits

1. Clear test organization: Easy to identify what level of testing is being performed
2. Issue kubeconfig is not persisted #28 prevention: Integration tests specifically validate kubeconfig persistence to prevent similar bugs
3. Better CI/CD: Different test types can be run at different pipeline stages
4. Maintainability: Each test type serves a clear purpose and can be run independently

Testing

All test suites pass:

• Unit tests: go test ./cmd/... ./internal/...
• API tests: go test ./test/api/...
• Integration tests: go test ./test/integration/...

The integration tests are designed to work without real AWS credentials by testing the application's behavior when credentials are unavailable, ensuring they can run in any CI environment.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Separate tests and add integration(e2e) tests </issue_title>
<issue_description>Currently, the unit tests for internal parts and exposed API are combined:

• separate internal tests from API tests (API test can be in another package)
• add some integration(e2e) tests if possible to check basic functionality (aws list/aws update). There was a bug kubeconfig is not persisted #28 where we did everything right but the kubeconfig was not persisted

</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #36

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