feat(snippets): add link to slack

[wJoenn]

Summary of changes and context

Small PR to add a "discuss this solution" button on snippets (currently only visible if the snippet's user is not the current user and if the snippet user has linked its Slack account) to be redirected to an existing thread, or a newly created thread if non existed, for the given snippet.

An additional condition was mentioned about only allowing users to generate 1 thread per hour but I'm not convince about that solution tbh

• firstly because if I want to ask 2 questions at once and those are the only one for the next 4 days I don't think that should be prevented
• having to come back again an hour later would probably deter the user from asking at all
• finally it's likely that sometimes the thread already exists so there's no reason to prevent a user from clicking on that button then, but it would also be a bad UX imo to sometimes click on a button and be redirected to a thread because it already exists, and sometimes be given an error saying I created too many thread for now. The user doesn't know how the button work, they just want to be redirected to Slack

Sanity checks

• [x] Linters pass
• [x] Tests pass
• [x] Related GitHub issues are linked in the description
• [x] Merge conflicts are resolved

[pil0u]

An additional condition was mentioned about only allowing users to generate 1 thread per hour but I'm not convince about that solution tbh

Je suis d'accord, on verra à l'usage 👍

[pil0u]

Closes #514

(edit : c'était déjà link en fait my bad 👀)