Merge branch '387837-slack-links' into 'master'

Sanitize slack-formatted links in chat messages

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/126744



Merged-by: George Koltsov <gkoltsov@gitlab.com>
Approved-by: Bojan Marjanovic <bmarjanovic@gitlab.com>
Approved-by: George Koltsov <gkoltsov@gitlab.com>
Reviewed-by: George Koltsov <gkoltsov@gitlab.com>
Reviewed-by: Bojan Marjanovic <bmarjanovic@gitlab.com>
Co-authored-by: carlad-gl <cdrago@gitlab.com>