Both realtime channel closes when subscribing to a channel that already exists

[dshukertjr]

Describe the bug
When listening to a channel that already has a subscription, both the first subscription and the second subscription closes. With the js library, only the first one closes and the second one remains connected.

To Reproduce
Steps to reproduce the behavior:

1. Subscribe to the same channel twice

  supabase.channel('channel').on(...).subscribe(); // This one closes
  supabase.channel('channel').on(...).subscribe(); // This one also closes, but should actually remain connected.

Expected behavior
The last connection made to the same channel should remain connected.

supabase_flutter version:

• Version [e.g. 1.0.0-dev.9]

Additional context
Also, it is not very apparent that you can only have 1 connection per channel. Maybe we can add more commented docs about it.

[Vinzent03]

I actually can't reproduce this currently. Did you encounter this yourself, or was it just because of my comment here? I can't remember xD.

I think my test was wrong, because we remove all channels in the tearDown in a group I likely tested this in.