Skip plus tests on a fork

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.

Author: sjberman

.github/workflows/ci.yml

@@ -234,6 +234,12 @@ jobs:
             "${{ needs.vars.outputs.min_k8s_version }}",
             "${{ needs.vars.outputs.k8s_latest }}",
           ]
+        isFork:
+          - ${{ github.event.repository.fork == true }}
+        exclude:
+          - {isFork: true}
+        include:
+          - {image: nginx}
     uses: ./.github/workflows/functional.yml
     with:
       image: ${{ matrix.image }}
@@ -255,6 +261,12 @@ jobs:
             "${{ needs.vars.outputs.k8s_latest }}",
           ]
         enable-experimental: [true, false]
+        isFork:
+          - ${{ github.event.repository.fork == true }}
+        exclude:
+          - {isFork: true}
+        include:
+          - {image: nginx}
     uses: ./.github/workflows/conformance.yml
     with:
       image: ${{ matrix.image }}
@@ -276,6 +288,12 @@ jobs:
             "${{ needs.vars.outputs.min_k8s_version }}",
             "${{ needs.vars.outputs.k8s_latest }}",
           ]
+        isFork:
+          - ${{ github.event.repository.fork == true }}
+        exclude:
+          - {isFork: true}
+        include:
+          - {image: nginx}
     uses: ./.github/workflows/helm.yml
     with:
       image: ${{ matrix.image }}