kube: clean up SimpleIngress

Rename `target_service` to `target` to mirror Service's `target`; rename `extra_paths` to `extraPaths` to follow the camelCase convention used everywhere except for a few places in kube.upstream (assumed to be a mistake)

Change-Id: Icfcb70ef889e3359bf0391c465034817f4b70cce
Reviewed-on: https://gerrit.hackerspace.pl/c/hscloud/+/1809
Reviewed-by: q3k <q3k@hackerspace.pl>
diff --git a/app/inventory/prod.jsonnet b/app/inventory/prod.jsonnet
index d54ba9d..4b9a150 100644
--- a/app/inventory/prod.jsonnet
+++ b/app/inventory/prod.jsonnet
@@ -85,6 +85,6 @@
 
   ingress: ns.Contain(kube.SimpleIngress(cfg.name)) {
     hosts:: [cfg.domain],
-    target_service:: top.service,
+    target:: top.service,
   },
 }