rabbitmq: Deploy RabbitMQ Server

RabbitMQ is an AMQP message broker.  It will be used by `xactmon` to
pass messages between the components.

Although RabbitMQ can be deployed in a high-availability cluster, we
don't really need that level of robustness for `xactmon`, so we will
just run a single instance.  Deploying a single-host RabbitMQ server
is pretty straightforward.

We're using mTLS authentication; clients need to have a certificate
issued by the *RabbitMQ CA* in order to connect to the message broker.
The `rabbitmq-ca` _cert-manager_ ClusterIssuer issues these certificates
for in-cluster services like `xactmon`.

rabbitmq/ca/kustomization.yaml

@@ -0,0 +1,12 @@
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+labels:
+- pairs:
+    app.kubernetes.io/component: rabbitmq-ca
+    app.kubernetes.io/instance: rabbitmq-ca
+    app.kubernetes.io/part-of: rabbitmq
+
+resources:
+- rabbitmq-ca.yaml
+- secrets.yaml