title: NestJs get request instance or execution context in custom validator (class validator)
body: <p>Is it possible to inject execution context or access current request in nestJs (class-validator => custom validator) ?</p>
  
  <pre class="lang-js prettyprint-override"><code>import { ValidatorConstraint, ValidatorConstraintInterface, ValidationArguments } from 'class-validator';
  import { Injectable } from '@nestjs/common';
  import { Connection } from 'typeorm';
  import { InjectConnection } from '@nestjs/typeorm';
  
  @ValidatorConstraint({ name: 'modelExistsConstraint', async: true })
  @Injectable()
  export class ModelExistsConstraint implements ValidatorConstraintInterface {
  
    constructor(
      @InjectConnection('default') private readonly connection: Connection,
    ) {
    }
  
    async validate(value: string, validationArguments: ValidationArguments) {
      // here need request or execution context;
      // const test = this.context.switchToHttp().getRequest();
      const model = await this.connection
        .getRepository(validationArguments.constraints[0])
        .findOne({ where: { [validationArguments.property]: value } });
      return !model;
    }
  
    defaultMessage(args: ValidationArguments) {
      return `Model with "${args.property}" - "${args.value}" already exists`;
    }
  }
  </code></pre>