input: Write a python function to generate a JSON response from given parameters.
  assert generate_response("name", "Alice") == '{"name": "Alice"}'
  assert generate_response("age", 30) == '{"age": 30}'
  assert generate_response("city", "New York") == '{"city": "New York"}'
output: import json
  
  def generate_response(key, value):
      return json.dumps({key: value})