[fix] Add schema validation for metrics

lib/refrepo/valid/input/schemas/schema-cluster.yaml

@@ -5,3 +5,4 @@ created_at: required # string or date ?
 kavlan: boolean
 queues: array
 priority: optional_string
+metrics: optional_array

lib/refrepo/valid/input/schemas/schema-network_equipments.yaml

@@ -56,3 +56,4 @@ channels:
       uid: string
       kind: string
       rate: integer
+metrics: optional_array

lib/refrepo/valid/input/schemas/schema-site.yaml

@@ -71,6 +71,7 @@ pdus:
       mac: optional_string
       vendor: optional_string
       model: optional_string
+      metrics: optional_array
       sensors:
         <array>:
           power: