fix: only do a Docker Login if the secrets are available

Author: Sam Harrison

.github/workflows/test-and-deploy.yml

@@ -17,11 +17,20 @@ jobs:
     timeout-minutes: 20
     strategy:
       matrix:
-        java: [8, 11]
+        java: [ 8, 11 ]
+    env:
+      DOCKER_LOGIN: ${{ secrets.DOCKER_USERNAME && secrets.DOCKER_AUTH_TOKEN }}
     steps:
       - name: Checkout sendgrid-java
         uses: actions/checkout@v2
 
+      - name: Login to Docker Hub
+        if: env.DOCKER_LOGIN
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.DOCKER_USERNAME }}
+          password: ${{ secrets.DOCKER_AUTH_TOKEN }}
+
       - name: Run Unit Tests
         run: make test-docker version=${{ matrix.java }}