code: function generateKey() {
  	let result = '';
  	for(let i=0; i<16; i++) {
  		let idx = Math.floor(Math.random() * CHARS.length);
  		result += CHARS[idx];
  	}
  	return result;
  }
docs: Generate a key for use with the local developer API. This does not generate
  a secure key, but the Mi Home app does not seem to do that either.