kube/postgres: force explicit versioning, storage class, clean up

Postgres version should be stated explicitly by the user. We can't auto-upgrade all apps, so we'd never change the 10.4 default. By forcing version to be explicit, we encourage users to pick the latest version when they first deploy, or to upgrade to latest from the old 10.4.

Also, non-existent storage class default is removed in favor of explicitly asking for storageClassName.

Change-Id: I715bcde6a66ca97be757abcea93c14139d61ed5a
Reviewed-on: https://gerrit.hackerspace.pl/c/hscloud/+/1791
Reviewed-by: informatic <informatic@hackerspace.pl>
diff --git a/app/matrix/lib/matrix.libsonnet b/app/matrix/lib/matrix.libsonnet
index dbf27d9..d13d620 100644
--- a/app/matrix/lib/matrix.libsonnet
+++ b/app/matrix/lib/matrix.libsonnet
@@ -85,6 +85,7 @@
     postgres3: ns.Contain(postgres) {
         cfg+: {
             appName: "synapse",
+            version: "10.4",
             database: "synapse",
             username: "synapse",
             prefix: "waw3-",