Add CONTRIBUTING.md (#366)

This patch adds a contribution guide to provide information on how to
become a contributor and how code changes should be submitted.

fixes: #211

---------

Co-authored-by: Gabriel Cocenza <[email protected]>

CONTRIBUTING.md

@@ -0,0 +1,72 @@
+# Contributing to Charmed OpenStack Upgrader (COU)
+
+Thank you for your interest in helping us improve **COU**! We're open to
+community contributions, suggestions, fixes, and feedback. This documentation
+will assist you in navigating through our processes.
+
+Make sure to review this guide thoroughly before beginning your contribution. It
+provides all the necessary details to increase the likelihood of your contribution
+being accepted.
+
+COU is hosted and managed on [GitHub](https://github.com). If you're new to GitHub
+and not familiar with how it works, their
+[quickstart documentation](https://docs.github.com/en/get-started/quickstart)
+provides an excellent introduction to all the tools and processes you'll need
+to know.
+
+## Prerequisites
+
+Before you can begin, you will need to:
+
+* Read and agree to abide by our
+  [Code of Conduct](https://ubuntu.com/community/code-of-conduct).
+
+* Sign the Canonical
+  [contributor license agreement](https://ubuntu.com/legal/contributors). This
+  grants us your permission to use your contributions in the project.
+
+* Create (or have) a GitHub account.
+
+* If you're working in a local environment, it's important to create a signing
+  key, typically using GPG or SSH, and register it in your GitHub account to
+  verify the origin of your code changes. For instructions on setting this up,
+  please refer to
+  [Managing commit signature verification](https://docs.github.com/en/authentication/managing-commit-signature-verification).
+
+## Code contribution
+If you're interested in making code contributions, please begin by forking the
+repository to your own GitHub account. From there, you can open Pull Requests (PRs)
+against the `main` branch of the upstream repository.
+
+Please adhere to the following guidelines prior to submitting your changes: 
+
+- Add or update any unit tests accordingly if applicable.
+- Format code with `make reformat` (which runs `black` and `isort`)
+- Ensure unit tests and/or linting checks pass by running `make lint` and
+  `make unittests`
+  - For documentation contribution, run the following commands and confirm that
+  - no errors are raised:
+    ```bash
+    cd docs/
+    make clean
+    make html
+    make spelling
+    make woke
+    make linkcheck
+    ``` 
+- Commit messages should be well-structured and provide a meaningful explanation
+  of the changes made
+- Commits must be signed (refer to the [Prerequisites](#prerequisites) section)
+
+## Find issues to work on
+[GitHub Issues](https://github.com/canonical/charmed-openstack-upgrader/issues)
+is our central hub for bug tracking and issue management, with labels used to
+organize them into different categories. For new contributors, we recommend
+starting with issues labeled "good first issue." If you're interested in
+enhancing our documentation, you can filter issues using the "documentation"
+label to find issues specifically related to documentation improvement.
+  
+Once you have decided which issue to work on, you can express your interest by
+posting a comment on it. When you submit your proposed fix for an issue, link
+your PR to the issue with one of the supported
+[keywords](https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue#linking-a-pull-request-to-an-issue-using-a-keyword).

docs/index.rst

@@ -37,6 +37,19 @@ In this documentation
 
       **Additional information** - details of upgrade phases and scopes defined in **COU**
 
+---------
+
+Project and community
+---------------------
+
+COU is a member of the Ubuntu family. It's an open source project that
+warmly welcomes community contributions, suggestions, fixes and
+constructive feedback.
+
+* We follow the Ubuntu community `Code of conduct`_
+* Contribute to the project on `GitHub`_ (documentation contributions go under
+  the **docs/** directory)
+* GitHub is also our central hub for bug tracking and issue management
 
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