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/store.go

@@ -2,11 +2,10 @@ package game
 
 import (
 	"context"
-	"crypto/rand"
-	"encoding/hex"
 	"sync"
 
 	"github.com/ryanhamamura/c4/db/repository"
+	"github.com/ryanhamamura/c4/player"
 )
 
 type PlayerSession struct {
@@ -40,7 +39,7 @@ func (gs *GameStore) makeNotify(gameID string) func() {
 }
 
 func (gs *GameStore) Create() *GameInstance {
-	id := GenerateID(4)
+	id := player.GenerateID(4)
 	gi := NewGameInstance(id)
 	gi.queries = gs.queries
 	gi.notify = gs.makeNotify(id)
@@ -107,12 +106,6 @@ func (gs *GameStore) Delete(id string) error {
 	return nil
 }
 
-func GenerateID(size int) string {
-	b := make([]byte, size)
-	_, _ = rand.Read(b)
-	return hex.EncodeToString(b)
-}
-
 type GameInstance struct {
 	game    *Game
 	gameMu  sync.RWMutex
@@ -166,7 +159,7 @@ func (gi *GameInstance) GetGame() *Game {
 	return gi.game
 }
 
-func (gi *GameInstance) GetPlayerColor(pid PlayerID) int {
+func (gi *GameInstance) GetPlayerColor(pid player.ID) int {
 	gi.gameMu.RLock()
 	defer gi.gameMu.RUnlock()
 	for _, p := range gi.game.Players {