Feature/ft categories on off setup

[soraiayugulis]

Summary

Phase 0 of the ft-categories-on-off feature — library integration and configuration. Adds the feature-gate-middleware library with GitHub Packages authentication, configures feature flag properties, and creates a FakeFeatureFlagClient for offline testing without ConfigCat SDK key.

Changes

Configuration

• pom.xml: Added GitHub Packages repository, feature-gate-middleware dependency (0.1.0-SNAPSHOT), and spring-boot-starter-actuator for Micrometer metrics
• application.yml: Added feature-gate.configcat.sdk-key, feature-gate.watch.enabled, and feature-gate.hi.enabled properties
• pr-validation.yml: Added GITHUB_TOKEN environment variable to test job for GitHub Packages authentication

Test Infrastructure

• FakeFeatureFlagClient.java: In-process stub implementation of FeatureFlagClient backed by Map<String, Boolean> for offline testing
• FakeFeatureFlagClientTest.java: 4 unit tests covering default behavior, flag setting, and unknown flags
• FeatureFlagTestConfiguration.java: Spring configuration providing FakeFeatureFlagClient as @Primary bean
• application-test.yml: Test profile configuration with feature-gate auto-configuration disabled
• BaseIntegrationTest.java: Base class for integration tests with @Import(FeatureFlagTestConfiguration.class) and @ActiveProfiles("test")
• FeatureFlagContextLoadTest.java: Context load test verifying FakeFeatureFlagClient is loaded without ConfigCat SDK key
• ApiIntegrationTest.java: Extended from BaseIntegrationTest to inherit feature flag test configuration

Notes

• Package Correction: The library uses io.architecture.featureflag.core package, not io.featuregate.core as initially documented in the spec
• Scope Override: feature-gate-middleware dependency scope set to compile to make API classes available for test compilation (library POM has all dependencies as runtime)
• Actuator Dependency: Added spring-boot-starter-actuator to provide MeterRegistry bean required by watchFeatureFlagAspect
• All Tests Pass: 120 tests passing with FakeFeatureFlagClient replacing ConfigCatFeatureFlagClient in test context

Checklist

• GitHub Packages repository configured in pom.xml
• feature-gate-middleware dependency added
• GITHUB_TOKEN env added to CI workflow
• application.yml configured with feature-gate properties
• FakeFeatureFlagClient implemented with unit tests
• FeatureFlagTestConfiguration bean created
• application-test.yml with feature-gate disabled
• BaseIntegrationTest for global test configuration
• Integration tests extended to use BaseIntegrationTest
• All 120 tests passing