Add Discourse and GitHub links to deprecation warnings

[ShivamRajSri]

This PR improves the deprecation warning message shown by warn_deprecation() in aiida/common/warnings.py.
It now includes links to AiiDA’s Discourse forum and GitHub issue tracker so that users can more easily report bugs or unexpected behavior.

Example output:
This feature is deprecated (this will be removed in v3)

If you encounter unexpected behavior or bugs, please report them via:
Discourse: https://aiida.discourse.group
GitHub: https://github.com/aiidateam/aiida-core/issues

Closes #6912

[danielhollas]

I am not sure this is good idea. @ShivamRajSri has this been discussed somewhere?

[ShivamRajSri]

Thanks for the feedback, @danielhollas!
Yes — this change is based on the Good First Issue titled “Add link to Discourse and GitHub in warning” (#issue-number:#6912
).
I implemented the improvement as described there — to include the Discourse and GitHub links in the deprecation warning message so users can easily report bugs or unexpected behavior.
Please let me know if there’s any preferred formatting or additional context I should include. Happy to adjust it as needed!

[danielhollas]

I see. There is a bit of a misunderstanding of the issu, this should not be added to the deprecation message. Rather, the Github/Discourse links should be added to the already existing "If you encounter unexpected behavior or bugs, please report them via Discourse or GitHub." which already exists in a couple of places (you can grep/search for "Discourse" to find them, for example in src/aiida/cmdline/commands/cmd_process.py.

[ShivamRajSri]

Thanks a lot for the clarification, @danielhollas!
You’re right - I misunderstood the issue scope.
I’ll update the existing warning messages (like in cmd_process.py) to include the proper Discourse and GitHub links instead of changing the deprecation warning.
I’ll push the fix shortly.

[ShivamRajSri]

Thanks for clarifying, @danielhollas!
I checked for other occurrences and found this message only in src/aiida/cmdline/commands/cmd_process.py.
I’ve updated it to include the full Discourse and GitHub links as suggested.
Please let me know if there are any other places you’d like me to update.