Agent - 4.5.0

This release adds support for local (per-rule) holdouts and Feature Rollouts, delivered by upgrading the embedded go-sdk from v2.3.0 to v2.5.0. It builds on the global holdouts support introduced in 4.4.0.

• Local Holdouts Support (#464): Agent now supports local (per-rule) holdouts in addition to global holdouts, via go-sdk v2.5.0. Local holdouts target specific rules and are evaluated per-rule, after forced decisions and before audience/traffic checks. Held-out decisions return enabled: false, variationKey: "ho_off_key", and ruleKey set to the holdout identifier, with impression rule_type: "holdout". As with global holdouts, all decision logic is handled by go-sdk — no Agent code changes are required beyond updating the ProjectConfig test mock.
• Feature Rollout Support (#463): Via go-sdk v2.4.0, Agent now supports Feature Rollouts — a rule type combining Targeted Delivery with A/B test measurement capabilities.

These changes come from the go-sdk v2.4.0 → v2.5.0 upgrade:

• Decision event ID normalization: decision event campaign_id and entity_id fall back to experiment_id when empty, and variation_id serializes as null when non-numeric, for cross-SDK consistency.
• ODP identify guard: ODP identify events carrying only a single identifier are now blocked.
• Removed legacy flag-level holdout fields from datafile parsing.

• Upgrade go-sdk v2.3.0 → v2.5.0 (#459, #463, #464)
• Add Dependabot to auto-update the go-sdk dependency (#458)
• Remove Coveralls from CI checks (#462)
• Add Agent developer documentation (#461)
• Fix Arnica security vulnerabilities (#460)
• Synchronize linters between go-sdk and agent (#457)
• Fix Dependabot alerts (#455, #456)

• Upgraded `github.com/optimizely/go-sdk/v2` from v2.3.0 to v2.5.0