Added CONTRIBUTING.md

Signed-off-by: Helber Belmiro <helber.belmiro@gmail.com>

CONTRIBUTING.md

@@ -0,0 +1,71 @@
+# Contributing guide
+
+**Want to contribute? Great!** We try to make it easy, and all contributions, even the smaller ones, are more than welcome. This includes bug reports, fixes, documentation, examples... But first, read this page.
+
+## Reporting an issue
+
+This project uses GitHub issues to manage the issues. Open an issue directly in GitHub.
+
+If you believe you found a bug, and it's likely possible, please indicate a way to reproduce it, what you are seeing, and
+what you would expect to see. Don't forget to indicate your Quarkus, Java, Maven/Gradle, and GraalVM versions.
+
+## Tests and documentation are not optional
+
+Don't forget to include tests in your pull requests. Also don't forget the documentation (reference documentation, javadoc...).
+
+### RESTEasy Reactive and RESTEasy Classic
+
+This extension supports RESTEasy Reactive and RESTEasy Classic. We have one profile for each implementation. By default, tests are run with RESTEasy Classic.
+
+#### Using the RESTEasy Reactive profile
+
+To run the tests using RESTEasy Reactive, use the `resteasy-reactive` [profile](https://github.com/quarkiverse/quarkus-openapi-generator/blob/32d9bd753724065d7217defb3085a734fea40bc8/integration-tests/pom.xml#L79), like the following:
+
+```shell
+mvn verify -Presteasy-reactive
+```
+
+#### Using the RESTEasy Classic profile
+
+To run the tests using RESTEasy Classic, use the `resteasy-classic` [profile](https://github.com/quarkiverse/quarkus-openapi-generator/blob/32d9bd753724065d7217defb3085a734fea40bc8/integration-tests/pom.xml#L49), like the following:
+
+```shell
+mvn verify -Presteasy-classic
+```
+
+#### Specific tests for each implementation
+
+Most of the tests are the same for both RESTEasy implementations, but a few of them require different code, like the `multipart-request` [integration test](https://github.com/quarkiverse/quarkus-openapi-generator/tree/main/integration-tests/multipart-request). For these cases, we have one test for each implementation, using the `org.junit.jupiter.api.Tag` annotation to specify the profile for each of them.
+
+### Code Style
+
+Maven automatically formats code and organizes imports when you run `mvn verify`. So, we recommend you do that before sending your PR. Otherwise, PR checks will fail.
+
+## Quarkus 3 and Quarkus 2 support
+
+This extension supports versions 3 and 2 of Quarkus and the code base is different for each Quarkus version. Therefore, we have the `main` branch supporting Quarkus 3, and the `quarkus2` branch supporting Quarkus 2. Preferably send your PRs to the `main` branch and [we will backport them to the `quarkus2` branch](#backporting-between-branches).
+
+## For the maintainers
+
+### Backporting between branches
+
+[We have a GitHub action for backporting PRs between different branches](.github/workflows/pr-backporting.yml). To use that, you must set a label named `backport-<destination_branch_name>`.
+
+Let's say you want to backport a PR from the `main` branch to the `quarkus2` branch. You would have to add a label named `backport-quarkus2` to the original PR. When that PR is merged, the GitHub actions bot will send a copy of the PR to the `quarkus2` branch.
+
+See an example:
+
+* [Original PR](https://github.com/quarkiverse/quarkus-openapi-generator/pull/439)
+* [Backport PR](https://github.com/quarkiverse/quarkus-openapi-generator/pull/445)
+
+#### Known limitation
+
+GitHub does not initiate checks for pull requests opened by the GitHub Actions bot. Therefore, [when we backport a PR to another branch the PR checks are not run automatically](https://github.com/quarkiverse/quarkus-openapi-generator/issues/450).
+
+### Backlog
+
+We have a [Kanban board](https://github.com/orgs/quarkiverse/projects/2), which is currently visible only by members of the [Quarkiverse organization](https://github.com/quarkiverse).
+
+### Staling issues and PRs
+
+We have a [GitHub action to automatically close issues and PRs](.github/workflows/stale_issues.yml) that didn't have interactions for a while. If you want to disable it for a specific issue or PR, you can add the `pinned` label and it will never stale.

README.md

@@ -19,6 +19,8 @@ project: https://opencollective.com/openapi_generator/donate
 
 This extension is for REST code generation for client side only. If you're looking for code generation for the server side, please take a look at the [Quarkus Apicurio Extension](https://github.com/Apicurio/apicurio-codegen/tree/main/quarkus-extension).
 
+**Want to contribute? Great!** We try to make it easy, and all contributions, even the smaller ones, are more than welcome. This includes bug reports, fixes, documentation, examples... But first, read [this page](CONTRIBUTING.md).
+
 ## Getting Started
 
 Add the following dependency to your project's `pom.xml` file: