We were incorrectly generating URLs with message id even when it was not provided, resulting in a route ending with "undefined", which was causing an error.
This commit also uses this opportunity to:
- move `invite_users` into a proper controller inside the API namespace
- refactors the code into a service: `Chat::InviteUsersToChannel`
While very fast and powerful staged threads forces a lot of gymnastic and edge cases. This patch adds a new service `Chat::CreateThread` and uses it to create a thread unconditionally when a user replies to a message in a threading enabled channel. If the user actually doesn’t send a message we will have a thread with no messages which has no important impact and could even be periodically cleaned if necessary.
Note that this commit also moves message actions to .gjs as it was the original goal of this PR to correctly check for staged thread to show the menu or not.
