input: Write a python function to add two numbers using Flask and handle the POST request.
  assert add_numbers({'num1': 3, 'num2': 5}) == {'sum': 8}
  assert add_numbers({'num1': 10, 'num2': 20}) == {'sum': 30}
  assert add_numbers({'num1': -1, 'num2': 1}) == {'sum': 0}
output: from flask import Flask, request, jsonify
  
  app = Flask(__name__)
  
  @app.route('/add_numbers', methods=['POST'])
  def add_numbers():
      data = request.get_json()
      num1 = data.get('num1')
      num2 = data.get('num2')
      result = {'sum': num1 + num2}
      return jsonify(result)
  
  if __name__ == '__main__':
      app.run()