Mark inbox commands with 'use' directive

This is an example that shows how to use this directive.

priv/graphql/schemas/admin/inbox.gql

@@ -1,28 +1,28 @@
 """
 Allow admin to flush the inbox bin".
 """
-type InboxAdminMutation @protected{
+type InboxAdminMutation @use(modules: ["mod_inbox"]) @protected{
   "Flush the user's bin and return the number of deleted rows"
   flushUserBin(
     "User to clear a bin"
     user: JID!,
     "Remove older than given days or all if null"
     days: PosInt
-  ): Int @protected(type: DOMAIN, args: ["user"])
+  ): Int @use(arg: "user") @protected(type: DOMAIN, args: ["user"])
 
   "Flush the whole domain bin and return the number of deleted rows"
   flushDomainBin(
     "Domain to be cleared"
     domain: String!,
     "Remove older than given days or all if null"
     days: PosInt
-  ): Int @protected(type: Domain, args: ["domain"])
+  ): Int @use(arg: "domain") @protected(type: Domain, args: ["domain"])
 
   "Flush the global bin and return the number of deleted rows"
   flushGlobalBin(
     "Required to identify the DB backend"
     hostType: String!,
     "Remove older than given days or all if null"
     days: PosInt
-  ): Int @protected(type: GLOBAL)
+  ): Int @use(arg: "hostType") @protected(type: GLOBAL)
 }

priv/graphql/schemas/user/inbox.gql

@@ -1,10 +1,10 @@
 """
 Allow user to flush own inbox bin".
 """
-type InboxUserMutation @protected{
+type InboxUserMutation @use(modules: ["mod_inbox"]) @protected{
   "Flush the user's bin and return the number of deleted rows"
   flushBin(
     "Remove older than given days or all if null"
     days: PosInt
-  ): Int 
+  ): Int @use
 }