add validation for group class

src/faction/faction.dto.ts

@@ -9,6 +9,7 @@ import {
   Max,
   IsOptional,
   IsHexColor,
+  IsIn,
 } from 'class-validator';
 
 import { GameEntity } from '../game/game.entity';
@@ -57,6 +58,8 @@ export class GameGroupDTO {
   @IsString()
   @Length(3, 31)
   name: string;
+  @IsIn(['infantry', 'recon', 'mechanized'])
+  class: string;
   @IsUUID('4')
   faction: FactionEntity;
 }