Refactor contribution serializer and validation

lib/utils/validator.js

@@ -0,0 +1,15 @@
+const tv4 = require('tv4');
+const validator = tv4.freshApi();
+
+validator.addFormat({
+  'date': function(value) {
+    const dateRegexp = /^[0-9]{4,}-[0-9]{2}-[0-9]{2}$/;
+    return dateRegexp.test(value) ? null : "A valid ISO 8601 full-date string is expected";
+  },
+  'time': function(value) {
+    const timeRegexp = /^([01][0-9]|2[0-3]):([0-5][0-9]):([0-5][0-9]|60)(\.[0-9]+)?(([Zz])|([\+|\-]([01][0-9]|2[0-3]):[0-5][0-9]))$/;
+    return timeRegexp.test(value) ? null : "A valid ISO 8601 full-time string is expected";
+  }
+})
+
+module.exports = validator;