Change workflow to use digest hash rather than 'latest'.

Author: Potherca

.github/workflows/ci.yml

@@ -1,6 +1,10 @@
 ---
 name: Solid Test Suites
 
+env:
+  PUBSUB_TAG: latest@sha256:35166933e3d30bde801fd156bd2f21ebba9cdeca464ebd574c6be4cdb14d35cd
+  COOKIE_TAG: latest@sha256:c71a3947f97d96ce09823743182582e0d919738be0d4ef5c8c55a9c22c615b91
+
 on:
   push:
     branches:
@@ -58,15 +62,20 @@ jobs:
 
       - name: Pull docker Images
         run: |
-          docker pull michielbdejong/nextcloud-cookie
+          docker pull michielbdejong/nextcloud-cookie:${{ env.COOKIE_TAG }}
           docker pull ${{ matrix.test }}
           docker pull ghcr.io/pdsinterop/solid-nextcloud:${{ github.sha }}
-          docker pull ghcr.io/pdsinterop/php-solid-pubsub-server:latest
+          docker pull ghcr.io/pdsinterop/php-solid-pubsub-server:${{ env.PUBSUB_TAG }}
 
       - name: Start Docker Containers
         run: |
           docker network create testnet
-          docker run -i --network=testnet -d --name 'pubsub' "ghcr.io/pdsinterop/php-solid-pubsub-server:latest"
+          docker run \
+            --detach \
+            --interactive \
+            --name 'pubsub' \
+            --network=testnet \
+            "ghcr.io/pdsinterop/php-solid-pubsub-server:${{ env.PUBSUB_TAG }}"
 
           source ./run-solid-test-suite.sh
           startSolidNextcloud 'server' "ghcr.io/pdsinterop/solid-nextcloud:${{ github.sha }}" ${{ matrix.test }}