feat: make Unix domain socket path and mode configurable

[pypingou]

Make the datarouter Unix domain socket configurable via environment variables while maintaining backward compatibility (defaults to abstract namespace with "datarouter_socket" path).

This enables containerized deployments where both the datarouter and applications run in separate containers and communicate via file-based sockets with shared volume mounts. Also supports running multiple datarouter instances with unique abstract namespace sockets.

Changes:

• Add socket_config module for centralized socket configuration
• Support DATAROUTER_SOCKET_PATH environment variable (default: "datarouter_socket")
• Support DATAROUTER_SOCKET_MODE environment variable ("abstract" or "file", default: "abstract")
• Update socketserver to use configurable socket address
• Add comprehensive unit tests (9 tests, all passing)
• Platform-specific defaults: Linux uses abstract, QNX uses file-based

Environment variables:

• DATAROUTER_SOCKET_PATH: Socket path (e.g., "/var/run/datarouter.sock" or "custom_socket")
• DATAROUTER_SOCKET_MODE: "abstract" for abstract namespace or "file" for filesystem-based

Example usage for containerized datarouter + application:

Both containers set:

export DATAROUTER_SOCKET_PATH=/var/run/datarouter.sock
export DATAROUTER_SOCKET_MODE=file

And mount the same volume at /var/run

Notes for Reviewer

Pre-Review Checklist for the PR Author

• PR title is short, expressive and meaningful
• Commits are properly organized
• Relevant issues are linked in the References section
• Tests are conducted
• Unit tests are added

Checklist for the PR Reviewer

• Commits are properly organized and messages are according to the guideline
• Unit tests have been written for new behavior
• Public API is documented
• PR title describes the changes

Post-review Checklist for the PR Author

• All open points are addressed and tracked via issues

References

Closes #

[github-actions]

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[github-actions]

The created documentation from the pull request is available at: docu-html

[arsibo]

please come to our FT meeting to discuss
We want to focus on QM Toolchain first. See https://github.com/orgs/eclipse-score/discussions/2757#:~:text=for%20logging%20is-,first,-QM%20Infrastructure%20shall

[pypingou]

@arsibo Sorry for the late reply. Joining meeting is not the most practical thing for me. Is there a possibility/place where we could have this discussion asynchronously?

[pypingou]

@anmittag I'm a little confused about this MR being assigned to me. Isn't the assignee supposed to do something with this MR?
Could you help me understand what is expected of me?

[anmittag]

Well @pypingou you have started a pr. I am expecting a pr author to follow up or accompany the pr till closure.

[pypingou]

@anmittag ok, for me the assignee would be more the reviewer rather than the author, but ok that's fine.

I'm unclear what the next steps are though. I've asked if there is an asynchronous alternative to attending the logging meeting and so far without answer.

Let's just discuss in this PR first and resort to a meeting only if we really need a higher-bandwidth mode of communication? Is there anything in this PR that is not clear to you?

[anmittag]

@pypingou no reviewers are mentioned separately