GitLab

- return TeamDTO with participants instead of participations
- change date management & add test to launch automatically
- display url to join a team

- add possibility to input price for each user & calculate automatically the mean price for the team
- remove errors on first display of team & participation
- add team creation with automatic participation creation

- add OneToMany relationship from team to participations
- add service to get the lists of teams that the logged user joined, display this list on home page
- add possibility to launch the secret santa
- add popup to discover one's receiver