text: Title: CSRF token issue with POST
  Body: I have created a REST API with Blueprints and have even used Flask-WTF's CSRFProtect exempt, to ignore CSRF for this blueprint.
  But still i keep getting "message": "The CSRF token is missing.", when I use the POST method.
  It works fine with GET method.
  
  app = Flask(__name__)
  api_blueprint = Blueprint('api', __name__, url_prefix='/api/1')
  csrf_protect = CSRFProtect(app)
  csrf_protect.exempt(api_blueprint)
  api = Api(api_blueprint, version='1.0', title='Sample API', description='REST API for Sample')
  
  @ns.route('/helloworld')
  class Token(Resource):
      @ns.doc('Hello world API')
      @csrf_protect.exempt
      def post(self):
          current_app.logger.info('hello world service called')
          return jsonify({'message': 'hello world'})'
  
  
  