Make ContactsMixin available for plugins

[alehaa]

NetBox version

v4.1.10

Feature type

Other

Triage priority

I volunteer to perform this work (if approved)

Proposed functionality

1. Add ContactsMixin and related mixin classes (column, filterset, …) to the plugin documentation.
2. Add ObjectContactsView to feature-view auto-registration

Use case

Plugins may want to use contacts for custom models. Making the mixin class public for use in the API will prevent plugins from reinventing the wheel and better integrate with NetBox, as they can implement a consistent UI with the NetBox core.

Database changes

None.

External dependencies

None.