Adds ability to expire email verify token (#2216)

Author: cherukumilli

README.md

@@ -226,6 +226,17 @@ var server = ParseServer({
   // Enable email verification
   verifyUserEmails: true,
 
+  // if `verifyUserEmails` is `true` and
+  //     if `emailVerifyTokenValidityDuration` is `undefined` then
+  //        email verify token never expires
+  //     else
+  //        email verify token expires after `emailVerifyTokenValidityDuration`
+  //
+  // `emailVerifyTokenValidityDuration` defaults to `undefined`
+  //
+  // email verify token below expires in 2 hours (= 2 * 60 * 60 == 7200 seconds)
+  emailVerifyTokenValidityDuration = 2 * 60 * 60, // in seconds (2 hours = 7200 seconds)
+
   // set preventLoginWithUnverifiedEmail to false to allow user to login without verifying their email
   // set preventLoginWithUnverifiedEmail to true to prevent user from login if their email is not verified
   preventLoginWithUnverifiedEmail: false, // defaults to false