Group lucky draw Unique Identifier check

[xljiadahao]

For the org lucky draw, there is a chance one user join one group multiple times, then it will get higher chance to win the lucky draw. It's unfair to those folks who join the group only once.
Proposal:

1. define whether the group would like to add the feature that the participants need to have their unique identifier (such as corporation ID) or not.
2. once the group asks for the unique identifier, during joining the group, the system should check the unique key to avoid any duplication for the group.