chore: 🤖 add IsHexadecimal to signature value

Author: prashantasdeveloper

src/settlements/dto/offchain-signature.dto.ts

@@ -2,7 +2,7 @@
 
 import { ApiProperty, ApiPropertyOptional } from '@nestjs/swagger';
 import { SignerKeyRingType } from '@polymeshassociation/polymesh-sdk/types';
-import { IsEnum, IsOptional } from 'class-validator';
+import { IsEnum, IsHexadecimal, IsOptional } from 'class-validator';
 
 export class OffChainSignatureDto {
   @ApiProperty({
@@ -21,5 +21,6 @@ export class OffChainSignatureDto {
       '0x12e368f3f697aa51fabf9977244c3531059a23637d05e3122b08259d2127792dc27bc9fe1a12660c0ac74ca4bd520955901d54c76c25e747356c93161654f586',
   })
   @IsOptional()
+  @IsHexadecimal()
   readonly value?: `0x${string}`;
 }