fix: add validation decorators to conversation DTO

src/modules/admin-conversation/dto/index.ts

@@ -1,7 +1,17 @@
+import { IsOptional, IsString, MaxLength } from 'class-validator';
+import { ApiProperty } from '@nestjs/swagger';
+
 export class CreateConversationDto {
+  @ApiProperty({ required: false })
+  @IsOptional()
+  @IsString()
+  @MaxLength(200)
   title?: string;
 }
 
 export class UpdateConversationDto {
-  title?: string;
+  @ApiProperty()
+  @IsString()
+  @MaxLength(200)
+  title: string;
 }