[Feature] Delete a subscription from a connection

[ysfscream]

Discussed in #1636

^{Originally posted by ton3r April 25, 2024}
It seems that I need to be connected to mqtt to remove a subscription.

But I have now the Problem that I am not allowed to subscribe to the subscription anymore and the client disconnect. But then I am not able to remove the subscription because it says "not connected"

How to force this?

--Tom