fix: validating string date in request body

Author: stampaaaron

apps/backend/src/research/participants/participant.dto.ts

@@ -1,13 +1,13 @@
 import { ApiProperty, OmitType, PartialType } from "@nestjs/swagger";
 import { Type } from "class-transformer";
-import { IsDate, IsOptional } from "class-validator";
+import { IsDateString, IsOptional } from "class-validator";
 
 export class ParticipantDto {
   @ApiProperty({ example: 1, description: "The id of the participant (child id)" })
   id: number;
 
   @ApiProperty({ example: "2024-11-01T00:05:02.718Z", description: "The birthday of the participant" })
-  @IsDate()
+  @IsDateString()
   @IsOptional()
   birthday?: Date;