NethLink: allow Audio/Video device configuration in NethLink

[edospadoni]

Currently, audio (headset, microphone) and video (camera) devices can only be configured through the CTI or Phone Island interface. It would be beneficial to allow direct configuration of these devices from NethLink before the call starts.

This is particularly useful for Bluetooth or wireless devices that do not automatically connect or are not immediately recognized. Users must wait until the call begins to select the correct device, often leading to confusion and improper device settings during the call.

Feature Request:
Introduce a feature in NethLink to configure and test audio (headset, microphone) and video (camera) devices prior to initiating the call.

Use Cases:
• Bluetooth headsets that connect with delay
• Quickly changing the default audio/video device
• Reducing setup errors and call disruptions due to device misconfiguration

Reference: https://partner.nethesis.it/t/nethvoice-1-3-0-click-to-call-con-scorciatoia-da-tastiera-per-nethlink/9341/3

[edospadoni]

Testing release:

• NS8-NethVoice: https://github.com/nethesis/ns8-nethvoice/releases/tag/1.3.4-testing.8
• NethLink: feat: add preferred devices management nethlink#64 (comment)