feat(mastodon): Add Pod-Anti-Affinity to improve HA setup

This patch uses pod anti-affinity to spread the mastodon pods throughout the
cluster this should ensure that a single node failure doesn't take down the
entire thing.

Adding PDBs will be done down the line.

apps/base/mastodon/release.yaml

@@ -73,12 +73,27 @@ spec:
               name: mastodon-streaming
             spec:
               replicas: 2
+              affinity:
+                podAntiAffinity:
+                  requiredDuringSchedulingIgnoredDuringExecution:
+                    - labelSelector:
+                        matchLabels:
+                          app.kubernetes.io/component: streaming
+                      topologyKey: kubernetes.io/hostname
           - kind: Deployment
             apiVersion: apps/v1
             metadata:
               name: mastodon-web
             spec:
               replicas: 2
+              affinity:
+                podAntiAffinity:
+                  requiredDuringSchedulingIgnoredDuringExecution:
+                    - labelSelector:
+                        matchLabels:
+                          app.kubernetes.io/component: web
+                          app.kubernetes.io/part-of: rails
+                      topologyKey: kubernetes.io/hostname
           - kind: ConfigMap
             apiVersion: v1
             metadata: