refactor: extract shared player.ID type and GenerateID to player package

Both game and snake packages had identical PlayerID types and the snake
package imported game.GenerateID. Now both use player.ID and
player.GenerateID from the shared player package.

game/persist.go

@@ -4,6 +4,7 @@ import (
 	"context"
 
 	"github.com/ryanhamamura/c4/db/repository"
+	"github.com/ryanhamamura/c4/player"
 
 	"github.com/rs/zerolog/log"
 )
@@ -109,19 +110,19 @@ func gameFromRow(row *repository.Game) (*Game, error) {
 func playersFromRows(rows []*repository.GamePlayer) []*Player {
 	players := make([]*Player, 0, len(rows))
 	for _, row := range rows {
-		player := &Player{
+		p := &Player{
 			Nickname: row.Nickname,
 			Color:    int(row.Color),
 		}
 
 		if row.UserID != nil {
-			player.UserID = row.UserID
-			player.ID = PlayerID(*row.UserID)
+			p.UserID = row.UserID
+			p.ID = player.ID(*row.UserID)
 		} else if row.GuestPlayerID != nil {
-			player.ID = PlayerID(*row.GuestPlayerID)
+			p.ID = player.ID(*row.GuestPlayerID)
 		}
 
-		players = append(players, player)
+		players = append(players, p)
 	}
 	return players
 }