Team creation workflow

[Nagarian]

Currently users need to declare their team when they create their account, however it's painful since the teamname is case sensitive and each year, I need to manually reorganize people in order to make them in the same team.
Also, since there is no team entity (and neither no user-id) all the aggregations made for the statistics and scoreboard are made by using those data (username, teamname) which has lead to the proto injection issue (see #38 )

So we need to rework that workflow.

Suggestion 1

Participants have suggested that to take something similar to CTFd

Suggestion 2

On the register page, we could make it as a two step forms

• step 1
  • Register as a team leader
  • Register and join an existing team
  • Register as a guest
• step 2
  • For team leader, they will be able to specify a team name
  • For joiner, they will need to specify a valid team token
  • Guest will not be asked any team

This way, it kepts simple and avoid the creation of new pages.