NethVoice: Editing a certified provider trunk replaces Contact User and From User with phone number instead of username

[mgarra]

Description:
When creating a new trunk for a certified provider where the username differs from the phone number, the configuration is initially applied correctly.
In the Advanced section of the trunk, both the Contact User and From User fields are correctly set to the username.

However, if the same trunk is later edited from Lines → VoIP, even if all parameters are confirmed without any change, the system overwrites both the Contact User and From User fields with the phone number, replacing the original username.

Steps to reproduce:

1. Create a new VoIP trunk for a certified provider where the username ≠ phone number.
2. Verify that in Advanced, both Contact User and From User are correctly set to the username.
3. Edit the same trunk from Lines → VoIP and confirm the configuration.
4. Check the Advanced section again.

Expected behavior:
The Contact User and From User fields should remain set to the username after editing the trunk.

Actual behavior:
After editing, both fields are replaced with the phone number.

Notes:
This issue occurs even when no parameters are changed during the trunk edit.

[Stell0]

1.5.1-testing.2