Replace registeredOn params to Long (timestamp) instead of String (ISO_OFFSET_DATE_TIME)

...igbluebutton/core/apps/users/RegisterUserReqMsgHdlr.scala

...ebutton/core/apps/users/ValidateAuthTokenReqMsgHdlr.scala

...n/scala/org/bigbluebutton/core/models/GuestsWaiting.scala

...scala/org/bigbluebutton/core/models/RegisteredUsers.scala

.../org/bigbluebutton/core2/message/senders/MsgBuilder.scala

...ore2/message/senders/ValidateAuthTokenRespMsgSender.scala

...scala/org/bigbluebutton/core2/testdata/FakeTestData.scala

.../test/scala/org/bigbluebutton/core/AppsTestFixtures.scala

...ain/scala/org/bigbluebutton/common2/msgs/GuestsMsgs.scala

.../main/scala/org/bigbluebutton/common2/msgs/UsersMgs.scala

...i/guest-users/server/handlers/guestsWaitingForApproval.js

...l5/imports/api/users/server/handlers/validateAuthToken.js