docs: add AI Usage Policy to CONTRIBUTING.md

CONTRIBUTING.md

@@ -1,12 +1,35 @@
 # Contributing
 
-I am happy that you want to contribute to Pocket ID and help to make it better! All contributions are welcome, including issues, suggestions, pull requests and more.
+We are happy that you want to contribute to Pocket ID and help to make it better!
+
+## Before you start
+
+Before starting to work on a new feature, please open an issue first, or comment on an existing one, to discuss the implementation details. This saves you time and avoids the disappointment of having a PR closed later because the change doesn't fit the project's direction.
+
+### AI Usage Policy
+
+We have nothing against using AI tools to assist your development. But we've seen a growing number of pull requests that appear to be fully or largely AI-generated and submitted without genuine human review. These are difficult and time-consuming for maintainers to review, and they often waste everyone's time.
+
+To keep contributions reviewable and high-quality, please follow these guidelines when using AI tools.
+
+#### Guidelines for Using AI Tools
+
+1. **Understand every line.** You must be able to explain what your code does and why, in your own words. "The AI wrote it" is not an acceptable answer to a reviewer's question.
+2. **Test before submitting.** Review and test all code manually, as a human, before opening a PR. Don't trust the AI's claim that it works.
+3. **Write your own words.** Don't paste AI-generated text into issues, comments, or PR descriptions. Walls of generated text make discussions harder, not easier.
+4. **Disclose your usage.** Note in the PR description how you used AI (see below).
+
+PRs that appear to be low effort AI output may be closed without a detailed review.
+
+#### Example disclosure
+
+> Used GitHub Copilot for autocomplete, and asked an LLM to help draft the test cases in `parser_test.go`. I reviewed, edited, and tested everything myself and understand how it works.
+
+> Used an LLM to generate the initial implementation of the new API endpoint, but I manually reviewed and tested it before submitting.
 
 ## Getting started
 
-You've found a bug, have suggestion or something else, just create an issue on GitHub and we can get in touch.
-
-## Submit a Pull Request
+### Submit a Pull Request
 
 Before you submit the pull request for review please ensure that
 
@@ -29,15 +52,15 @@ Before you submit the pull request for review please ensure that
 - Your pull request has a detailed description
 - You run `pnpm format` to format the code
 
-## Development Environment
+### Development Environment
 
 Pocket ID consists of a frontend and backend. In production the frontend gets statically served by the backend, but in development they run as separate processes to enable hot reloading.
 
 There are two ways to get the development environment setup:
 
-### 1. Install required tools
+#### 1. Install required tools
 
-#### With Dev Containers
+##### With Dev Containers
 
 If you use [Dev Containers](https://code.visualstudio.com/docs/remote/containers) in VS Code, you don't need to install anything manually, just follow the steps below.
 
@@ -46,7 +69,7 @@ If you use [Dev Containers](https://code.visualstudio.com/docs/remote/containers
 3. VS Code will detect .devcontainer and will prompt you to open the folder in devcontainer
 4. If the auto prompt does not work, hit `F1` and select `Dev Containers: Open Folder in Container.`, then select the pocket-id repo root folder and it'll open in container.
 
-#### Without Dev Containers
+##### Without Dev Containers
 
 If you don't use Dev Containers, you need to install the following tools manually:
 
@@ -54,9 +77,9 @@ If you don't use Dev Containers, you need to install the following tools manuall
 - [Go](https://golang.org/doc/install) >= 1.26
 - [Git](https://git-scm.com/downloads)
 
-### 2. Setup
+#### 2. Setup
 
-#### Backend
+##### Backend
 
 The backend is built with [Gin](https://gin-gonic.com) and written in Go. To set it up, follow these steps:
 
@@ -64,7 +87,7 @@ The backend is built with [Gin](https://gin-gonic.com) and written in Go. To set
 2. Copy the `.env.development-example` file to `.env` and edit the variables as needed
 3. Start the backend with `go run -tags exclude_frontend ./cmd`
 
-### Frontend
+##### Frontend
 
 The frontend is built with [SvelteKit](https://kit.svelte.dev) and written in TypeScript. To set it up, follow these steps:
 
@@ -77,9 +100,13 @@ You're all set! The application is now listening on `localhost:3000`. The backen
 
 ### Testing
 
+If you are contributing to a new feature please ensure that you add tests for it.
+
+#### End-to-end tests
+
 We are using [Playwright](https://playwright.dev) for end-to-end testing.
 
-If you are contributing to a new feature please ensure that you add tests for it. The tests are located in the `tests` folder at the root of the project.
+The tests are located in the `tests` folder at the root of the project.
 
 The tests can be run like this:
 
@@ -93,3 +120,9 @@ The tests can be run like this:
 5. Run the tests with `pnpm dlx playwright test` or from the root project folder `pnpm test`
 
 If you make any changes to the application, you have to rebuild the test environment by running `docker compose up -d --build` again.
+
+#### Unit tests
+
+In the backend we are using unit tests with the built-in Go testing framework. The tests are located in the same folder as the code they are testing and have the `_test.go` suffix.
+
+To run the tests, simply run `go test ./...` from the root of the `backend` folder.