chore: skip integration tests on forks (#692)

GitHub provides no reasonable and secure way to run integration tests
against PRs from forks. This PR adjusts the CI builds to skip
integration tests on PRs from forks and otherwise runs the entire test
suite for internal PRs. In addition, integration tests will run on main
regardless to catch any regressions.

.github/workflows/tests.yaml

@@ -45,6 +45,11 @@ jobs:
           CGO_ENABLED=0 GOOS=openbsd go build
   integration:
     runs-on: [self-hosted, linux, x64]
+    # run integration tests on all builds except pull requests from forks or
+    # dependabot
+    if: |
+      github.event_name != 'pull_request' ||
+      (github.event.pull_request.head.repo.full_name == github.repository && github.actor != 'dependabot[bot]')
     name: "integration tests (linux)"
     permissions:
       contents: 'read'