add JOI validation for constraint allowedRegistrants

Author: himaniraghav3

src/services/ChallengeService.js

@@ -1165,6 +1165,7 @@ createChallenge.schema = {
       tags: Joi.array().items(Joi.string()), // tag names
       projectId: Joi.number().integer().positive(),
       legacyId: Joi.number().integer().positive(),
+      constraints: Joi.array().items(Joi.string()).min(1).optional(),
       startDate: Joi.date().iso(),
       status: Joi.string().valid([
         constants.challengeStatuses.Active,
@@ -1991,6 +1992,7 @@ updateChallenge.schema = {
       tags: Joi.array().items(Joi.string().required()).min(1), // tag names
       projectId: Joi.number().integer().positive(),
       legacyId: Joi.number().integer().positive(),
+      constraints: Joi.array().items(Joi.string()).min(1).optional(),
       status: Joi.string().valid(_.values(constants.challengeStatuses)),
       attachments: Joi.array().items(
         Joi.object().keys({