fix: correct success status codes on Management Interface endpoints

[matlec]

Description

This is a spec hygiene fix.

The Device Capabilities endpoint documented 201 OK for every successful write. That reason phrase does not exist (201 is Created, 200 is OK), and a single 201 was used for both creating and updating a document. Per RFC 9110, 201 Created is correct only when a new resource is created. An update should return 200 OK. This meant a client updating an device that was already registered received 201, reporting a creation that never happened.

This PR aligns the Management Interface endpoints on a single convention: 201 Created on creation, 200 OK on update, 204 No Content on delete.

Issues Addressed

#195

Change Type

Please select the relevant options:

• Fix (change that resolves an issue)
• New enhancement (change that adds specification content)
• Content edits (change that edits existing content)

Checklist

• I have read the CONTRIBUTING document.
• My changes adhere to the established patterns, and best practices.

[github-actions]

❌ @matlec the signed-off-by was not found in the following 1 commits:

• df13590: Merge branch 'pre-draft' into fix/capabilities-http-status

📝 What should I do to fix it?

All proposed commits should include a sign-off in their messages, ideally at the end.

❔ Why it is required

The Developer Certificate of Origin (DCO) is a lightweight way for contributors to certify that they wrote or otherwise have the right to submit the code they are contributing to the project. Here is the full text of the DCO, reformatted for readability:

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.

Contributors sign-off that they adhere to these requirements by adding a Signed-off-by line to commit messages.

This is my commit message

Signed-off-by: Random Developer <randomdeveloper@example.com>

Git even has a -s command line option to append this automatically to your commit message:

$ git commit -s -m 'This is my commit message'