Build a simple URL shortener in a preferably JVM-based language (e.g. Java, Kotlin).

It should:

• Accept a full URL and return a shortened URL.
• A shortened URL should have a randomly generated alias.
• Allow a user to customise the shortened URL if they want to (e.g. user provides my-custom-alias instead of a random string).
• Persist the shortened URLs across restarts.
• Expose a decoupled web frontend built with a modern framework (e.g., React, Next.js, Vue.js, Angular, Flask with templates). This can be lightweight form/output just to demonstrate interaction with the API. Feel free to use UI frameworks like Bootstrap, Material-UI, Tailwind CSS, GOV.UK design system, etc. to speed up development.
• Expose a RESTful API to perform create/read/delete operations on URLs.
  → Refer to the provided openapi.yaml for API structure and expected behaviour.
• Include the ability to delete a shortened URL via the API.
• Have tests.
• Be containerised (e.g. Docker).
• Include instructions for running locally.

• Fork the repository and work in your fork. Do not push directly to the main repository.
• There is no time limit, we want to see something you are proud of. We would like to understand roughly how long you spent on it though.
• Commit often with meaningful messages.
• Write tests.
• The API should validate inputs and handle errors gracefully.
• The Frontend should show errors from the API appropriately.
• Use the provided openapi.yaml as the API contract.
• Focus on clean, maintainable code.
• AI tools (e.g., GitHub Copilot, ChatGPT) are allowed, but please do not copy-paste large chunks of code. Use them as assistants, not as a replacement for your own work. We will be asking.

• Working software.
• Decoupled web frontend (using a modern framework like React, Next.js, Vue.js, Angular, or Flask with templates).
• RESTful API matching the OpenAPI spec.
• Tests.
• A git commit history that shows your thought process.
• Dockerfile.
• README with:
  • How to build and run locally.
  • Example usage (frontend and API).
  • Any notes or assumptions.