This is the result to complete the Exercise URL Shortener Microservice project. Instructions for building this project can be found at https://www.freecodecamp.org/learn/back-end-development-and-apis/back-end-development-and-apis-projects/url-shortener-microservice

 * Avoid duplicate original Url
 * Avoid duplicate short Url
 * Using local file to save user input

• You should provide your own project, not the example URL.
• You can POST a URL to /api/shorturl and get a JSON response with original_url and short_url properties. Here's an example: { original_url : 'https://freeCodeCamp.org', short_url : 1}
• When you visit /api/shorturl/<short_url>, you will be redirected to the original URL.
• If you pass an invalid URL that doesn't follow the valid http:https://www.example.com format, the JSON response will contain { error: 'invalid url' }