📌(docker) replace minio by silo

The quay.io/minio/minio and quay.io/minio/mc images now answer 401, and
the minio images are gone from Docker Hub as well: the dev stack, the
backend CI job and the helm dev-backend could not pull them anymore.

[pgsty/silo](https://hub.docker.com/r/pgsty/silo) and
[pgsty/mc](https://hub.docker.com/r/pgsty/mc) are community builds and drop
in replacement of minio. Only the executable name is changing from minio
to silo.

.github/workflows/impress.yml

@@ -175,13 +175,13 @@ jobs:
 
       - name: Start MinIO
         run: |
-          docker pull quay.io/minio/minio
+          docker pull pgsty/silo
           docker run -d --name minio \
             -p 9000:9000 \
             -e "MINIO_ACCESS_KEY=impress" \
             -e "MINIO_SECRET_KEY=password" \
             -v /data/media:/data \
-            quay.io/minio/minio server --console-address :9001 /data
+            pgsty/silo server --console-address :9001 /data
 
       # Tool to wait for a service to be ready
       - name: Install Dockerize
@@ -194,7 +194,7 @@ jobs:
 
       - name: Configure MinIO
         run: |
-          MINIO=$(docker ps | grep minio/minio | sed -E 's/.*\s+([a-zA-Z0-9_-]+)$/\1/')
+          MINIO=$(docker ps | grep pgsty/silo | sed -E 's/.*\s+([a-zA-Z0-9_-]+)$/\1/')
           docker exec ${MINIO} sh -c \
             "mc alias set impress http://localhost:9000 impress password && \
             mc alias ls && \