Allow websocket connection to be active as in foreground mode

[Tin-Primas]

Is your feature request related to a problem? Please describe.
Receive calls and keep connection while still in background

Describe the solution you'd like
The app will run in foreground mode and because there will be a notification for foreground mode user can swipe it right to disable it.
So we will have probably another flag when create the helper

allowForegroundMode: false // by default

Describe alternatives you've considered
I have considered using flutter background service but the websocket connection is close so even if i tried to keep the SipUAListener active there is no active connection to be listen on

Additional context
This functionality is really needed because on the phone no one will use softphone unless it can listen even if it's terminated