feat: seperate single and multi choice questions

src/modules/submissions/dtos/answer-submission.dto.ts

@@ -1,4 +1,4 @@
-import { IsNumber, IsOptional } from 'class-validator';
+import { IsArray, IsInt, IsNumber, IsOptional } from 'class-validator';
 import { SubmissionAnswer } from '../decorators/submission-answer.decorator';
 
 export class AnswerSubmissionDTO {
@@ -6,6 +6,11 @@ export class AnswerSubmissionDTO {
   @IsOptional()
   choiceId?: number;
 
+  @IsArray()
+  @IsOptional()
+  @IsInt({ each: true })
+  choiceIds?: number[];
+
   @IsNumber()
   @IsOptional()
   numericValue?: number;