Secret Santa (シークレットサンタ)

To begin with, what is Secret Santa...
A group of people are asked to exchange gifts with each other.
The game is to exchange gifts with a group of people by randomly deciding who will give gifts to whom.
By keeping the sender of the gifts a secret, there is also the fun of revealing spoilers after the gifts have been received.
This application provides the following functions to make planning a Secret Santa event simple and easy.
* Create a group to exchange gifts.
* Invite and join groups using invitation URLs (notification when group members join)
* Start the gift exchange (notification at the start of the event)
* Secret Santa spoilers