Transfer portal

[mautamu]

Story:

As a user, I want to be able to see when someone has joined or new team after elimination so that I can prepare my forces accordingly.

Technical design:

Database:

• Add table user_updates
• Add columns id UUID, type ENUM (playing_for, current_team, streak), effective_date timestamp without time zone DEFAULT CURRENT_TIMESTAMP, season integer, day integer, agent Text, from: integer null, to: integer not_null

Rust Risk:

• Add crate https://github.com/adwhit/diesel-derive-enum
• Add enum user::UserUpdate with variants NewUser, PlayingFor, CurrentTeam
• Add endpoint /api/transfers?<season: optional>&<day: optional> that returns:

[{
    "player": String,
    "season": Integer,
     "day": Integer,
    "from": Nullable<TeamInfo>,
    "to": TeamInfo,
}]

• Filter api returns to only include playing_for changes
• On new team joins (see this), submit a user_update.