Add Serial Number to Avahi Service for Board Deduplication

[mirkoCrobu]

Motivation

A board connected via both USB and Network currently shows up as two separate devices in the board list. This makes it difficult for a client application to know it is the same physical board.

We need a way to "deduplicate" these entries by providing a common identifier, allowing the client to show just one entry for that board.

Change description

A simple approach is to add the board's serial number to its Avahi service file. This change will be made at runtime when the EnableNetworkMode function is executed.

Specifically, we will add a new containing the serial number (e.g., serial_number=YOUR_SERIAL) to the board's .service file.

Additional Notes

Reviewer checklist

• PR addresses a single concern.
• PR title and description are properly filled.
• Changes will be merged in main.
• Changes are covered by tests.
• Logging is meaningful in case of troubleshooting.

[lucarin91]

I didn't figure out that we needed to add another sudoers file for this feature, which I would avoid to do it. So I think we should change the approach here, and we could instead do that in a systemd unit that is triggered only on the first boot, e.g., https://github.com/arduino/arduino-app-cli/blob/main/debian/arduino-app-cli/etc/systemd/system/arduino-burn-bootloader.service.
The Serial number of the board should not change, so we can do it just the first time you flash the board, and in there, you have all the permission to patch the Avahi service.

[mirkoCrobu]

How to test it

1. Create the .deb and push it into the board
   On the board
2. Be sure that /etc/avahi/services/arduino.service doesn't contain the serial number
3. Reboot the board
4. Check /etc/avahi/services/arduino.service: now you should see the serial number
5. Check that the .flag file exists: ls -l /var/lib/arduino/avahi_serial_configured.flag
6. Check the service status (should be active (exited)): systemctl status arduino-avahi-serial.service
7. Enable network mode: arduino-app-cli system network-mode enable
   From your PC
8. Check the board list configs(you should the network information with serial number:
   ): arduino-cli board list --json

[lucarin91]

I would also add the disable command in postrm as for the other services

[lucarin91]

LGTM, I would improve a little bit the schell script

[lucarin91]

@mirkoCrobu I think you need to update rebase main, I see changes not related to this PR

[mirkoCrobu]

@lucarin91 I had to change a commit author already includedd in main to pass license/cla.
Let me check if I can fix it

[lucarin91]

I think it is safe to always return errors