(Arch discussion required) Improve handling in contacts widget for atSigns which no longer exist

[gkc]

Which at_widget package you want to add enhancement?

at_contacts_flutter

On what platforms do you want to add enhancement?

Android, iOS, Windows, MacOS, Linux

Is your feature request related to a problem?

See atsign-foundation/at_client_sdk#458 (comment) for background

Describe the solution that you'd like

No response

Describe alternatives that you have considered

No response

Additional context

No response

[gkc]

@VJag as you were involved in the discussion on the original bug where it was suggested that we should improve the handling in the contacts widget, please could you re-familiarize yourself with the context so we can perhaps discuss this in one of next week's architecture calls?