Fix IRC mirror timeout when relaying messages

[Grimpper]

Fixes: The IRC mirror times out when relaying IRC messages to Zulip due to SSL
socket sharing between parent and child processes after forking with
'mp.Process'.

How did you test this PR?
I've ran the mirror connected to a small IRC room and verified that the messages
where correctly relayed back and forth between the Zulip Cloud Guix instance and
the IRC room. I've used the following command:

./pre-inst-env guix shell python-zulip -- zulip-irc-bridge --irc-server=irc.libera.chat --channel='#lapislazuli' --nick-prefix=irc_mirror --stream='libera.chat IRC' --site='https://guix.zulipchat.com' --user=irc-bot@guix.zulipchat.com --api-key=$API_KEY

Self-review checklist

• Self-reviewed the changes for clarity and maintainability
  (variable names, code reuse, readability, etc.).

Communicate decisions, questions, and potential concerns.

• Explains differences from previous plans (e.g., issue description).
• Highlights technical choices and bugs encountered.
• Calls out remaining decisions and concerns.
• Automated tests verify logic where appropriate.

Individual commits are ready for review (see commit discipline).

• Each commit is a coherent idea.
• Commit message(s) explain reasoning and motivation for changes.

Completed manual review and testing of the following:

• Visual appearance of the changes.
• Responsiveness and internationalization.
• Strings and tooltips.
• End-to-end functionality of buttons, interactions and flows.
• Corner cases, error conditions, and easily imagined bugs.

[emilysutherlin]

@Niloth-p would you be up for taking a look at this PR? Relevant CZO discussion here#zulip cloud > IRC mirror issues.

[Niloth-p]

Thanks for the PR! LGTM apart from a couple of possible improvements. Please do fix the linting errors in the second commit.

[Niloth-p]

The name fresh_session is not very readable when being passed to mp.Process. Maybe something like forward_zulip_to_irc might be better.

[Grimpper]

Done!

[Grimpper]

Please do fix the linting errors in the second commit.

I've done what I could. I'm not familiar with Python, so I don't know what else to do. If you know how to fix the lint errors, you can force push before merging. Thanks!

[Niloth-p]

Sorry for the delay in getting back. Thanks for the updates.

@laurynmm Could you please help assign an integration reviewer? The remaining mypy & gitlint fixes are listed below.

Remaining Linting Update - Diff

diff --git a/zulip/integrations/bridge_with_irc/irc_mirror.py b/zulip/integrations/bridge_with_irc/irc_mirror.py
index 8d9bbee5..e0370986 100755
--- a/zulip/integrations/bridge_with_irc/irc_mirror.py
+++ b/zulip/integrations/bridge_with_irc/irc_mirror.py
@@ -46,7 +46,7 @@ def main() -> None:
     options.client = "irc_mirror"
     zulip_client = zulip.init_from_options(options)
     try:
-        from .irc_mirror_backend import IRCBot # type: ignore[import-untyped]
+        from .irc_mirror_backend import IRCBot  # type: ignore[import-untyped]
     except ImportError:
         traceback.print_exc()
         print(

Commit messages - proposed replacements:

Commit 1 - description:

Ensure forked processes have a clean client to prevent sharing the
parent's SSL sockets.

Commit 2 - title + description:

integrations: Make IRC mirror integration script installable.

This change was originally proposed by Sharlatan Hellseher:
https://codeberg.org/guix/guix/pulls/7418#issuecomment-12239616

* Rename file `irc-mirror.py` to 'irc_mirror.py' to make it importable.
* Introduce the `main' entry point.
* Register 'zulip-irc-bridge' as a console script.