Save rank into database

[Azaret]

The idea is to save the player rank into the database instead of calculating it on ranking display.
This aim to solve the issue of losing ranking of old event when the ranking calculation change from one event to another.
For the back part, this should be done:

• Add nullable rank INT field on table account_event_status.
• Create new endpoint to update ranking (either one by one player, or all of them?).
• Add rank field on the endpoint /event/:id/users.

For the front part:

• Change sorting on rank field.
• Add refresh ranking admin action, which would update ranking for all players (should be hidden when the event is over).

[Azaret]

Side note: Since ranking calculation is done once, sorting and even the full ranking table could be done on the back side in SQL. EDIT: PIvot is too boring to do with mySQL, forget it.

[Azaret]

Added endpoint /event/:id/user/:id/rank with PUT method and payload:

{
  "rank": 0
}