Update workflow to exclude tests from external users. (#7539)

Author: granluo

.github/workflows/test_coverage.yml

@@ -7,6 +7,9 @@ on:
     # closed will be triggered when a pull request is closed.
     types: [opened, synchronize, closed]
 
+env:
+  METRICS_SERVICE_SECRET: ${{ secrets.GHASecretsGPGPassphrase1 }}
+
 jobs:
   check:
     if: github.repository == 'Firebase/firebase-ios-sdk' && (github.event.action == 'opened' || github.event.action == 'synchronize')
@@ -35,7 +38,10 @@ jobs:
         id: check_files
         env:
           pr_branch: ${{ github.event.pull_request.head.ref }}
-        run: ./scripts/code_coverage_report/get_updated_files.sh
+        run: |
+          if [ ! -z "${{ env.METRICS_SERVICE_SECRET }}"  ]; then
+          ./scripts/code_coverage_report/get_updated_files.sh
+          fi
 
   pod-lib-lint-database:
     needs: check
@@ -269,14 +275,12 @@ jobs:
 
   create_report:
     needs: [check, pod-lib-lint-abtesting, pod-lib-lint-auth, pod-lib-lint-database, pod-lib-lint-dynamiclinks, pod-lib-lint-firestore, pod-lib-lint-functions, pod-lib-lint-inappmessaging, pod-lib-lint-instanceid, pod-lib-lint-messaging, pod-lib-lint-performance, pod-lib-lint-remoteconfig, pod-lib-lint-storage]
-    env:
-      metrics_service_secret: ${{ secrets.GHASecretsGPGPassphrase1 }}
     if: always()
     runs-on: macOS-latest
     steps:
       - uses: actions/checkout@v2
       - name: Access to Metrics Service
-        if:  env.metrics_service_secret
+        if:  ${{ env.METRICS_SERVICE_SECRET }}
         run: |
           # Install gcloud sdk
           curl https://sdk.cloud.google.com > install.sh
@@ -286,14 +290,14 @@ jobs:
 
           # Activate the service account for Metrics Service.
           scripts/decrypt_gha_secret.sh scripts/gha-encrypted/metrics_service_access.json.gpg \
-          metrics-access.json "$metrics_service_secret"
+          metrics-access.json "${{ env.METRICS_SERVICE_SECRET }}"
           gcloud auth activate-service-account --key-file metrics-access.json
       - uses: actions/download-artifact@v2
         id: download
         with:
           path: /Users/runner/test
       - name: Compare Diff and Post a Report
-        if: github.event_name == 'pull_request' && env.metrics_service_secret
+        if: github.event_name == 'pull_request' && ${{ env.METRICS_SERVICE_SECRET }}
         env:
           base_commit: ${{ needs.check.outputs.base_commit }}
         run: |
@@ -304,7 +308,7 @@ jobs:
           swift run CoverageReportGenerator --presubmit "firebase/firebase-ios-sdk" --commit "${GITHUB_SHA}" --token $(gcloud auth print-identity-token) --xcresult-dir "/Users/runner/test/codecoverage" --log-link "https://github.com/firebase/firebase-ios-sdk/actions/runs/${GITHUB_RUN_ID}" --pull-request-num ${{github.event.pull_request.number}} --base-commit "$base_commit"
           fi
       - name: Update New Coverage Data
-        if: github.event.pull_request.merged == true && env.metrics_service_secret
+        if: github.event.pull_request.merged == true && ${{ env.METRICS_SERVICE_SECRET }}
         run: |
           if [ -d "${{steps.download.outputs.download-path}}" ]; then
           cd scripts/code_coverage_report/generate_code_coverage_report