Migrate CI from Travis to GitHub Actions (main branch)

[Copilot]

This PR migrates CI on main from Travis to GitHub Actions using the shared reusable workflows in logstash-plugins/.ci@1.x. The migration preserves Travis execution scope by porting only the test type actually present in the fully-resolved Travis config.

• Resolved Travis scope and parity mapping

  • .travis.yml imports logstash-plugins/.ci:travis/travis.yml@1.x (which imports defaults.yml, matrix.yml, exec.yml).
  • Resolved matrix indicates base unit-test jobs only for this plugin.
  • No INTEGRATION=true / SECURE_INTEGRATION=true signals on this repo’s config path.
  • Performance stage in shared Travis config is gated by HAS_PERFORMANCE_TESTS=1; this plugin does not set it.
  • Parity result: add only unit-tests workflow.

• GitHub Actions workflow added

  • Added .github/workflows/unit-tests.yml as a reusable-workflow caller to:
    • logstash-plugins/.ci/.github/workflows/unit-tests.yml@1.x
  • Includes required trigger set (push, pull_request, schedule, workflow_dispatch), schedule fan-out job, secrets: inherit, and timeout-minutes: 60.
  • Scheduled matrix is branch-scoped to active branch list for this plugin ([main]).

• README badge migration

  • Replaced Travis badge with GitHub Actions Unit Tests badge:
    • actions/workflows/unit-tests.yml/badge.svg?branch=main

• Travis retirement

  • Deleted .travis.yml.
  • No additional Travis-only directories/files were present.

jobs:
  tests:
    if: github.event_name != 'schedule'
    uses: logstash-plugins/.ci/.github/workflows/unit-tests.yml@1.x
    secrets: inherit
    with:
      timeout-minutes: 60

  scheduled:
    if: github.event_name == 'schedule'
    strategy:
      matrix:
        branch: [main]
    uses: logstash-plugins/.ci/.github/workflows/unit-tests.yml@1.x
    secrets: inherit
    with:
      ref: ${{ matrix.branch }}
      timeout-minutes: 60