Relationship support for model bulk edit

[lampwins]

Environment

• Python version: 3.8
• Nautobot version: 1.2.4

Proposed Functionality

As Nelly the Network Engineer, I want to be able to bulk edit the software version, which is a relationship from the DLM plugin, for a set of devices, so that I don't have to follow an unintuitive flow of going through the software model to change a device's software.

Use Case

Like #1317 and #1316 relationships are lacking several features that the average user would expect, given consistency in other areas.

This would likely not take advantage of #1593 once it is implemented due to the bulk nature of the modification.

Database Changes

We might need to look more deeply at the relationship model to support this.

External Dependencies

None

[lampwins]

Note that many-to-many relationships should show an "add" and "remove" multi-select field in the UI like how tags are implemented in the bulk form.

[glennmatthews]

Conceptually it seems like this would only make sense to include for many-to-many and many-to-one relationships (i.e. relationships where it's permissible for many different source objects to associate to the same destination object). I suppose for one-to-many and one-to-one relationships we could at least include a "delete" or "set null" checkbox though to allow bulk clearing of such a relationship?

[bryanculver]

Closed in #2014