Normalize the `PlayerModel` by extracting `position`, `team`, and `league` into separate tables

[nanotaboada]

Description

Refactor the Player schema by normalizing related fields (position, team, and league) into separate tables. This will improve data integrity and reduce redundancy.

ERD

DDL

CREATE TABLE IF NOT EXISTS "leagues" (
    "id" INTEGER PRIMARY KEY AUTOINCREMENT,
    "name" TEXT NOT NULL UNIQUE,
    "country" TEXT NOT NULL,
    "confederation" TEXT
);

CREATE TABLE IF NOT EXISTS "teams" (
    -- https://liaison.reuters.com/tools/sports-team-codes
    "id" TEXT PRIMARY KEY,
    "name" TEXT NOT NULL UNIQUE,
    "leagueId" INTEGER NOT NULL,
    FOREIGN KEY ("leagueId") REFERENCES "leagues"("id") ON UPDATE NO ACTION ON DELETE CASCADE
);

CREATE TABLE IF NOT EXISTS "positions" (
    "id" TEXT NOT NULL PRIMARY KEY,
    "name" TEXT NOT NULL,
    CHECK (
        id = 'GK' AND name = 'Goalkeeper'
        OR id = 'RB' AND name = 'Right-Back'
        OR id = 'LB' AND name = 'Left-Back'
        OR id = 'CB' AND name = 'Centre-Back'
        OR id = 'DM' AND name = 'Defensive Midfield'
        OR id = 'CM' AND name = 'Central Midfield'
        OR id = 'RW' AND name = 'Right Winger'
        OR id = 'AM' AND name = 'Attacking Midfield'
        OR id = 'CF' AND name = 'Centre-Forward'
        OR id = 'SS' AND name = 'Second Striker'
        OR id = 'LW' AND name = 'Left Winger'
    )
);

CREATE TABLE IF NOT EXISTS "players" (
    "id" INTEGER PRIMARY KEY AUTOINCREMENT,
    "firstName" TEXT NOT NULL,
    "middleName" TEXT,
    "lastName" TEXT NOT NULL,
    "dateOfBirth" TEXT,
    "squadNumber" INTEGER NOT NULL UNIQUE,
    "positionId" TEXT NOT NULL,
    "teamId" TEXT NOT NULL,
    "starting11" BOOLEAN,
    FOREIGN KEY ("positionId") REFERENCES "positions"("id") ON UPDATE NO ACTION ON DELETE NO ACTION,
    FOREIGN KEY ("teamId") REFERENCES "teams"("id") ON UPDATE NO ACTION ON DELETE NO ACTION
);

CREATE INDEX IF NOT EXISTS "idx_teams_leagueId" ON "teams"("leagueId");
CREATE INDEX IF NOT EXISTS "idx_players_positionId" ON "players"("positionId");
CREATE INDEX IF NOT EXISTS "idx_players_teamId" ON "players"("teamId");

Acceptance Criteria

• Create new tables with the proposed DDL script.
• Create new schemas for Position, Team, and League, defining relationships with the existing Player.
• Create new PositionModel, TeamModel and LeagueModel.
• Update existing the SQLAlchemy schemas, Pydantic models and FastAPI endpoints accordingly.
• Migrate existing data without breaking API functionality.