feat(volume): add "exchange volumes"

This volumes are "emptyDir" and can have init command. For example, in a
"same-pod", it allow the user to copy data from image to a directory
that is mounted on others pods.

generator/labels/katenaryLabels.go

@@ -32,6 +32,7 @@ const (
 	LabelConfigMapFiles Label = KatenaryLabelPrefix + "/configmap-files"
 	LabelCronJob        Label = KatenaryLabelPrefix + "/cronjob"
 	LabelEnvFrom        Label = KatenaryLabelPrefix + "/env-from"
+	LabelExchangeVolume Label = KatenaryLabelPrefix + "/exchange-volumes"
 )
 
 var (

generator/labels/katenaryLabelsDoc.yaml

@@ -284,4 +284,40 @@
         {{ .KatenaryPrefix }}/env-from: |-
             - myservice1
 
+"exchange-volumes":
+  short: Add exchange volumes (empty directory on the node) to share data
+  type: "list of objects"
+  long: |-
+    This label allows sharing data between containres. The volume is created in 
+    the node and mounted in the pod. It is useful to share data between containers
+    in a "same pod" logic. For example to let PHP-FPM and Nginx share the same direcotory.
+
+    This will create:
+    - an `emptyDir` volume in the deployment
+    - a `voumeMount` in the pod for **each container**
+    - a `initContainer` for each definition
+
+    Fields:
+      - name: the name of the volume (manadatory)
+      - mountPath: the path where the volume is mounted in the pod (optional, default is `/opt`)
+      - init: a command to run to initialize the volume with data (optional)
+
+    !!! Warning
+        This is highly experimental. This is mainly useful when using the "same-pod" label.
+
+  example: |-
+    nginx:
+      # ...
+      labels;
+        {{ .KatenaryPrefix }}/exchange-volumes: |-
+          - name: php-fpm
+            mountPath: /var/www/html
+    php:
+      # ...
+      labels:
+        {{ .KatenaryPrefix }}/exchange-volumes: |-
+          - name: php-fpm
+            mountPath: /opt
+            init: cp -ra /var/www/html/* /opt
+
 # vim: ft=gotmpl.yaml

generator/labels/labelStructs/exchangeVolume.go

@@ -0,0 +1,20 @@
+package labelStructs
+
+import "gopkg.in/yaml.v3"
+
+type ExchangeVolume struct {
+	Name      string `yaml:"name" json:"name"`
+	MountPath string `yaml:"mountPath" json:"mountPath"`
+	Type      string `yaml:"type,omitempty" json:"type,omitempty"`
+	Init      string `yaml:"init,omitempty" json:"init,omitempty"`
+}
+
+func NewExchangeVolumes(data string) ([]*ExchangeVolume, error) {
+	mapping := []*ExchangeVolume{}
+
+	if err := yaml.Unmarshal([]byte(data), &mapping); err != nil {
+		return nil, err
+	}
+
+	return mapping, nil
+}