[feature] Store openwisp-config and openwisp-monitoring versions per device

⚠️ Not suitable for new contributors

Is your feature request related to a problem? Please describe.

The controller currently does not persist the versions of the OpenWISP components running on each device. This makes it difficult to determine which devices are running outdated or incompatible versions of openwisp-config and openwisp-monitoring, and complicates upgrades, troubleshooting, and fleet-wide compatibility checks.

Describe the solution you'd like

Have the device report and the controller store the installed versions of:

• openwisp-config
• openwisp-monitoring

The version information should be updated whenever the device sends its regular status or information update, and exposed in the device admin and REST API so that users can inspect and filter devices by component version where practical.

The implementation should define how missing, unavailable, or unsupported component versions are represented and should remain backward compatible with devices that do not report these values.

Please also consider documenting the expected reporting format and adding tests for registration, subsequent updates, missing values, and both components being installed or unavailable.

Describe alternatives you've considered

Administrators can currently inspect devices individually or connect to them manually, but this does not provide a reliable, centralized view of component versions across a device fleet. Storing the values in the controller would make version inventory and upgrade planning much easier.

Additional context

This feature may require coordinated changes to the device-side reporting mechanism in openwisp-config and openwisp-monitoring, in addition to the controller model, API, and admin interface.

Start by tracing the regular device status or information update path and the controller's device model, REST API, and admin interface. Review the reporting mechanisms in openwisp-config and openwisp-monitoring to define how both versions and missing values are represented. Done means backward-compatible storage and exposure, coordinated device-side reporting, documentation, and tests for registration, updates, missing values, and unavailable components.