try signing seb server docker image

.github/workflows/buildReporting.yml

@@ -111,6 +111,9 @@ jobs:
       run: |
         echo $TAG_NAME
         echo ${{ env.TAG_NAME }}
+    - 
+       name: Install Cosign
+       uses: sigstore/cosign-installer@main
     -
       name: Set up QEMU
       uses: docker/setup-qemu-action@v1
@@ -140,4 +143,14 @@ jobs:
         file: ./docker/Dockerfile
         push: true
         tags: |
-          anhefti/seb-server:${{ env.TAG_NAME }}
+          anhefti/seb-server:${{ env.TAG_NAME }}
+    -
+      name: Sign image with a key
+      run: |
+        echo ${COSIGN_PRIVATE_KEY} > /tmp/my_cosign.key && \
+        cosign sign --key /tmp/my_cosign.key ${TAGS}
+        env:
+          TAGS: |
+            anhefti/seb-server:${{ env.TAG_NAME }}
+          COSIGN_KEY: ${{secrets.COSIGN_PRIVATE_KEY}}
+          COSIGN_PASSWORD: ${{secrets.COSIGN_PASSWORD}}