Do not suggest @all and @here if they are not allowed

[paulchen]

Is your feature request related to a problem? Please describe. When typing @, the list of suggestions always contain @all and @here:

However, in case permissions are configured to not allow them, messages using @all and/or @here will not be sent. Instead, an error message is shown:

Describe the solution you'd like In my opinion it makes sense to remove @all and/or @here from the list of suggestions in case they are not allowed.

[Barrylimarti]

Not sure about the need for it. If the maintainers can confirm the need I can work on this.