Rewrite [ElmPackage] (#2403)

Ref #1358

services/validators.js

@@ -1,6 +1,6 @@
 'use strict'
 
-const Joi = require('joi')
+const Joi = require('joi').extend(require('joi-extension-semver'))
 
 module.exports = {
   nonNegativeInteger: Joi.number()
@@ -10,4 +10,7 @@ module.exports = {
   anyInteger: Joi.number()
     .integer()
     .required(),
+  semver: Joi.semver()
+    .valid()
+    .required(),
 }