✨(backend) add url to download media attachments with access rights

We make use of nginx subrequests to block media file downloads while
we check for access rights. The request is then proxied to the object
storage engine and authorization is added via the "Authorization"
header. This way the media urls are static and can be stored in the
document's json content without compromising on security: access
control is done on all requests based on the user cookie session.

src/helm/env.d/dev/values.impress.yaml.gotmpl

@@ -103,3 +103,17 @@ ingressWS:
 ingressAdmin:
   enabled: true
   host: impress.127.0.0.1.nip.io
+
+ingressMedia:
+  enabled: true
+  host: impress.127.0.0.1.nip.io
+
+  annotations:
+    nginx.ingress.kubernetes.io/auth-url: https://impress.127.0.0.1.nip.io/api/v1.0/documents/retrieve-auth/
+    nginx.ingress.kubernetes.io/auth-response-headers: "Authorization, X-Amz-Date, X-Amz-Content-SHA256"
+    nginx.ingress.kubernetes.io/upstream-vhost: minio.impress.svc.cluster.local:9000
+    nginx.ingress.kubernetes.io/rewrite-target: /impress-media-storage/$1
+
+serviceMedia:
+  host: minio.impress.svc.cluster.local
+  port: 9000