Update contributors guidelines (keycloak#46904)

Signed-off-by: Bruno Oliveira da Silva <bruno@abstractj.com>
Co-authored-by: Václav Muzikář <vaclav@muzikari.cz>

Author: abstractj

CONTRIBUTING.md

@@ -38,7 +38,7 @@ not be able to respond to your PR immediately. The best place to ping us is on t
 
 If you would like to contribute to Keycloak, but are not sure exactly what to work on, you can find a number of open
 issues that are awaiting contributions in  
-[issues](https://github.com/keycloak/keycloak/issues).
+[issues](https://github.com/keycloak/keycloak/issues). To keep things manageable for everyone, new contributors may have at most 2 open pull requests at a time. This ensures you can focus on addressing review feedback promptly and helps reviewers manage their workload.
 
 ### Open a discussion on a proposed change
 
@@ -110,6 +110,18 @@ git commit --signoff --message "This is the commit message"
 
 This option adds a `Signed-off-by` trailer at the end of the commit log message.
 
+### Use of Generative AI
+
+Generative AI tools may be used to assist in writing code, tests, or documentation, provided that you fully understand every change you submit. The goal is to keep Keycloak's code consistent and high-quality while respecting reviewers' limited time.
+
+If you use generative AI to assist with your contribution, all of the following are required:
+
+1. **You understand the change.** You must be able to explain what your code does and why. Submitting AI-generated code you do not understand is not acceptable.
+2. **You engage with review feedback.** You are expected to respond to questions and comments from reviewers. If you use AI to help draft responses, you must edit and proofread them to ensure they are accurate and address the reviewer's point.
+3. **You can revise the code yourself.** If a reviewer requests changes, you are responsible for addressing them, even if your AI tool is unable to produce a suitable fix.
+4. **You disclose AI agents usage.** Include a note in the PR description indicating the usage of AI agents for generating complete solutions from a prompt (i.e. you do not need to mention a simple AI autocomplete). This helps reviewers calibrate their review. 
+5. **You ensure licensing compliance.** All generated code must be released under the [Apache License, Version 2.0](https://www.apache.org/licenses/LICENSE-2.0), the same license as Keycloak. You are responsible for verifying that the tools you use do not introduce additional licensing restrictions.
+
 ### Spotless
 
 Spotless is used to check and apply code formatting. To check your code locally before sending a PR run: