docs: document new podSettings key in SmbCommonConfig

The new podSettings key allows for control of certain parameters the
operator can not guess at. Currently, this allows one to control
scheduling via nodeSelector and affinity sections.

Signed-off-by: John Mulligan <[email protected]>

Author: phlogistonjohn

docs/resources/SmbCommonConfig.md

@@ -12,6 +12,12 @@ metadata:
 spec:
   network:
     publish: external
+  podSettings:
+    nodeSelector:
+      "kubernetes.io/os": "linux"
+      "kubernetes.io/arch": "amd64"
+    affinity:
+      ... <k8s affinity spec> ...
 ```
 
 ## Specification
@@ -22,10 +28,48 @@ spec:
     Publishing to `cluster` means that the Service is set up for in-cluster
     networking only. Publishing the resource `external` means that the
     Service will be configured as a LoadBalancer service.
+* `podSettings`: Optional settings controlling how pods created by the operator
+   are constructed.
+  * `nodeSelector`: Optional map of Kubernetes labels to values.
+    Equivalent to the pod spec value of the same name.
+    See https://kubernetes.io/docs/concepts/scheduling-eviction/assign-pod-node/#nodeselector
+  * `affinity`: Optional specification controlling node affinity and pod affinities.
+    Equivalent to the pod spec value of the same name.
+    See https://kubernetes.io/docs/concepts/scheduling-eviction/assign-pod-node/#affinity-and-anti-affinity
 
 
 NOTE: A LoadBalancer Service requires support from the Kubernetes cluster to
 work. In the case of Kubernetes in the Cloud many providers automatically
 configured this feature. In the case of a bare-metal Kubernetes cluster you may
 need to set up and maintain your own load balancer. The samba-operator has been
 tested with [MetalLB](https://metallb.universe.tf/).
+
+
+Full example of an SmbCommonConfig with both node selector and node affinity
+settings applied:
+```yaml
+apiVersion: samba-operator.samba.org/v1alpha1
+kind: SmbCommonConfig
+metadata:
+  name: domain-security1
+  namespace: smb-shares
+spec:
+  network:
+    publish: external
+  podSettings:
+    nodeSelector:
+      "kubernetes.io/os": "linux"
+      "kubernetes.io/arch": "amd64"
+    affinity:
+      nodeAffinity:
+        preferredDuringSchedulingIgnoredDuringExecution:
+          - weight: 10
+            preference:
+              matchExpressions:
+                - key: storage-server
+                  operator: In
+                  values:
+                    - samba
+                    - smb
+                    - default
+```