NethVoice: Add RTSP protocol to NethVoice CTI Streaming

[andrea-marchionni]

In NethVoice CTI, I want to implement the following functionalities:

• Video Streaming: Display video streams from devices such as video intercoms.
• Gate Controls: Enable interaction with gate openings, supporting multiple gates per video intercom. Interaction can occur through a call to the gate using DTMF tones or via an Action URL (preferred, as it does not require a phone call). However, it is important always to evaluate reachability, possibly using the NethLink core as the click-to-call function.
• Streaming Previews: Provide a streaming preview within the incoming call notification.
• User Permissions: Allow administrators to decide which users can access this feature.

In the previous version, streaming support was limited to unauthenticated JPEG formats.
However, modern video intercoms, such as certain Fanvil models, utilize both authenticated and unauthenticated RTSP streaming.

Gate control can be managed via DTMF tones during calls or through action URLs.

This implementation should start with specific video intercom models, such as those from Fanvil, and expand as needed for RTSP protocol.