Skip plus tests on a fork (#2784)

Problem: The NGINX Plus JWT is only available on the upstream repo, so automated tests for Plus can't be run on forks.

Solution: Skip these test runs on a fork.

.github/workflows/conformance.yml

@@ -24,6 +24,7 @@ jobs:
   conformance-tests:
     name: Run Tests
     runs-on: ubuntu-24.04
+    if: ${{ !github.event.pull_request.head.repo.fork || inputs.image != 'plus' }}
     permissions:
       contents: write # needed for uploading release artifacts
     env:

.github/workflows/functional.yml

@@ -21,6 +21,7 @@ jobs:
   functional-tests:
     name: Run Tests
     runs-on: ubuntu-24.04
+    if: ${{ !github.event.pull_request.head.repo.fork || inputs.image != 'plus' }}
     env:
       DOCKER_BUILD_SUMMARY: false
     steps:

.github/workflows/helm.yml

@@ -17,7 +17,7 @@ jobs:
   helm-tests-local:
     name: Helm Tests Local
     runs-on: ubuntu-24.04
-    if: ${{ github.event_name != 'schedule' }}
+    if: ${{ github.event_name != 'schedule' && (!github.event.pull_request.head.repo.fork || inputs.image != 'plus') }}
     steps:
       - name: Checkout Repository
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2