Add CONTRIBUTING file with guidelines for contributing to the project

Signed-off-by: Fabian Mettler <[email protected]>

CONTRIBUTING.md

@@ -0,0 +1,94 @@
+# Contributing
+
+The Incus team appreciates contributions to the project, through pull requests, issues on the [GitHub repository](https://github.com/lxc/terraform-provider-incus/issues), or discussions or questions on the [forum](https://discuss.linuxcontainers.org).
+
+Check the following guidelines before contributing to the project.
+
+## Code of Conduct
+
+When contributing, you must adhere to the Code of Conduct, which is available at: [`https://github.com/lxc/terraform-provider-incus/blob/main/CODE_OF_CONDUCT.md`](https://github.com/lxc/terraform-provider-incus/blob/main/CODE_OF_CONDUCT.md)
+
+## License and copyright
+
+By default, any contribution to this project is made under the Mozilla Public License 2.0.
+
+The author of a change remains the copyright holder of their code
+(no copyright assignment).
+
+## Pull requests
+
+Changes to this project should be proposed as pull requests on GitHub
+at: [`https://github.com/lxc/terraform-provider-incus`](https://github.com/lxc/terraform-provider-incus)
+
+Proposed changes will then go through review there and once approved,
+be merged in the main branch.
+
+### Commit structure
+
+Separate commits should be used for:
+
+- Documentation (`docs: Update XYZ` for files in `docs/`)
+- Resources (`<resource>: Add XYZ` for changes to resources in `internal/`)
+- Tests (`tests: Add test for XYZ` for changes to `tests/`)
+
+This structure makes it easiser for contributions to be reviewed and also
+greatly simplifies the process of back-porting fixes to stable branches.
+
+### Developer Certificate of Origin
+
+To improve tracking of contributions to this project we use the DCO 1.1
+and use a "sign-off" procedure for all changes going into the branch.
+
+The sign-off is a simple line at the end of the explanation for the
+commit which certifies that you wrote it or otherwise have the right
+to pass it on as an open-source contribution.
+
+```
+Developer Certificate of Origin
+Version 1.1
+
+Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
+660 York Street, Suite 102,
+San Francisco, CA 94110 USA
+
+Everyone is permitted to copy and distribute verbatim copies of this
+license document, but changing it is not allowed.
+
+Developer's Certificate of Origin 1.1
+
+By making a contribution to this project, I certify that:
+
+(a) The contribution was created in whole or in part by me and I
+ have the right to submit it under the open source license
+ indicated in the file; or
+
+(b) The contribution is based upon previous work that, to the best
+ of my knowledge, is covered under an appropriate open source
+ license and I have the right under that license to submit that
+ work with modifications, whether created in whole or in part
+ by me, under the same open source license (unless I am
+ permitted to submit under a different license), as indicated
+ in the file; or
+
+(c) The contribution was provided directly to me by some other
+ person who certified (a), (b) or (c) and I have not modified
+ it.
+
+(d) I understand and agree that this project and the contribution
+ are public and that a record of the contribution (including all
+ personal information I submit with it, including my sign-off) is
+ maintained indefinitely and may be redistributed consistent with
+ this project or the open source license(s) involved.
+```
+
+An example of a valid sign-off line is:
+
+```
+Signed-off-by: Random J Developer <[email protected]>
+```
+
+Use a known identity and a valid e-mail address.
+Sorry, no anonymous contributions are allowed.
+
+We also require each commit be individually signed-off by their author,
+even when part of a larger set. You may find `git commit -s` useful.