docs: Update Kubernetes Secret backend docs

Signed-off-by: Dennis Lapchenko <dennis.lapchenko@gmail.com>

docs/backends.md

@@ -706,20 +706,27 @@ data:
   password: <path:secret-id#key | base64encode>
 ```
 
-### Kubernets Secret
+### Kubernetes Secret
 
-**Note**: The Kubernetes secret backend does not support versioning
+Setup the backend with default secret from which to conveniently inject values from.
+Optionally alternative secret names can be passed through path.
+
+**Note**: The Kubernetes Secret backend does not support versioning
 
 ##### Kubernetes Secret Authentication
 
-Refer to the "Configuring Plugin" section, as this backend uses same in-cluster service-account as the plugin itself.
+Backend inherits same in-cluster service-account as the plugin itself
 
 These are the parameters for Kubernetes Secret:
 
 ```
 AVP_TYPE: kubernetessecret
 AVP_K8S_SECRET_SECRET: avp-secret-data
 ```
+`AVP_K8S_SECRET_SECRET` can have namespace prefix, ie.:
+```
+AVS_K8S_SECRET_SECRET: prod:avp-secret-data
+```
 
 ##### Examples