Check user permission.
    ---
    request_serializer: serializers.CheckPerm

    parameters:
        - name: user
          type: string
          required: true
          description: username
          paramType: query

        - name: perm
          type: string
          required: true
          description: permission code
          paramType: query

    type:
        result:
            required: true
            type: string
            description: user have permission

    responseMessages:
        - code: 200
          message: User have permission

        - code: 400
          message: User have not permission

        - code: 401
          message: Unauthorized

def check_perm(request):
    """
    Check user permission.
    ---
    request_serializer: serializers.CheckPerm

    parameters:
        - name: user
          type: string
          required: true
          description: username
          paramType: query

        - name: perm
          type: string
          required: true
          description: permission code
          paramType: query

    type:
        result:
            required: true
            type: string
            description: user have permission

    responseMessages:
        - code: 200
          message: User have permission

        - code: 400
          message: User have not permission

        - code: 401
          message: Unauthorized
    """
    serializer = serializers.CheckPerm(data=request.query_params)
    serializer.is_valid(raise_exception=True)
    logger.debug('User have perm', extra=serializer.data)
    return Response({'result': 'ok'})