Migrate CI to GitHub Actions

[adam-rocska]

Summary

• Replace the Travis CI configuration with a GitHub Actions workflow.
• Remove the Travis-only Kafka setup script and Package-Builder path.
• Update README and generated docs badges from Travis CI to GitHub Actions.
• Constrain swift-log to 1.0.0..<1.2.0 so Swift 5.0.1 resolves a compatible dependency instead of the current release line.

Why

Travis CI is stale for this repository and the existing configuration depends on old Travis-specific environment behavior, Package-Builder, and inactive build infrastructure. Keeping it around adds noise without giving maintainers useful signal.

The new workflow keeps this first pass intentionally conservative. It uses Swift 5.0.1 in an Ubuntu Xenial container and Kafka/Zookeeper 5.2.2 service containers, matching the old support era instead of starting a Swift or platform modernization pass in the same change.

The dependency range change is part of restoring that baseline. swift-log is declared from 1.0.0, which lets SwiftPM resolve today to 1.12.0; that release no longer compiles under Swift 5.0.1. Capping the range keeps the old Swift support target reproducible without changing SwiftKafka source code.

Cost and operations

This workflow runs on the standard GitHub-hosted ubuntu-24.04 runner for a public repository. GitHub Actions minutes for standard GitHub-hosted runners are free for public repositories, and this workflow does not use larger runners, paid external CI services, or persistent artifacts/caches.

Validation

• Parsed .github/workflows/ci.yml as YAML locally.
• Parsed the updated SwiftPM manifest locally and verified the swift-log range resolves as 1.0.0..<1.2.0.
• Verified there are no remaining Travis, Package-Builder, or setupKafka references in the repository.
• Ran git diff --check successfully.
• GitHub Actions passed on this PR: Swift 5.0.1, Ubuntu Xenial container, Kafka/Zookeeper 5.2.2, swift build, and swift test.

Notes

This is not a full CI/platform modernization. The old Travis Swift development snapshot lane and macOS Xcode 10.2 lane are intentionally not recreated here. Those should be handled in a separate support-policy pass after the repository has a working baseline CI signal again.

[adam-rocska]

@LowAmmo @dannys42 or @mbarnach could one of you take a peek at it? Looks ok to me, but hey, I'm just blindly staring at the monitor. The more eyes see it the better.

[LowAmmo]

Hoping that sometime in the new future we would be able to remove the limit on the swift-log version.