Closes: #7854 - Add VDC/Instances/etc

[DanSheps]

Closes: #7854

This PR adds VDC/Instance/etc support to NetBox

• Adds VDC Model
• Adds vdc M2M field on Interfaces
• Adds vdc_type field to device_type

Not stuck on the names, could be renamed "VirtualDeviceInstance" easily enough to be more encompassing and less Ciscoy

[jeremystretch]

As noted in #7854, some VDC implementations permit the assignment of an interface to multiple VDCs whereas others do not. This might be something we want to track per VDC instance as a configurable attribute.

[DanSheps]

As noted in #7854, some VDC implementations permit the assignment of an interface to multiple VDCs whereas others do not. This might be something we want to track per VDC instance as a configurable attribute.

I can see a couple of options for tracking this, by a atribute on:

1. Device Type
2. Device
3. VDC
4. Interface
5. Interface.vdcs.through

For DeviceType, I think this makes the most sense. It allows you to define your Device as allowing interface sharing. Device seems like an awkward place to track this type of setting. VDC, typically either the platform (Nexus 7700 for example, which doesn't) allows VDC interface sharing or not. Interface, I think would be a great place for a "Shared Interface" checkbox but I don't think it would make sense to use this to track whether the platform allows sharing. Similar to "Device", I don't think the through model is the best place to track this

I think a combination of "Can interface share" on the device type and a "Shared inteface" attribute on the Interface is the best way go. We could infer whether it is a shared interface too, just based on how many VDC's are assigned (>1 == Shared), but there could be a case where the interface is set to allow sharing but currently only one device context is created.

Thoughts?

[jeremystretch]

I think we should avoid over-rotating on this, and just stick with permitting the assignment of an interface to multiple VDCs. If there's a strong need for some conditional logic there, I'm sure we'll hear of it during the beta evaluation.

[DanSheps]

Once thing I thought of... We may have a situation now where an interface needs to be created in a VDC but is not shared, we might need to investigate the uniqueness parameters for interfaces now and add VDC when VDC is not null as a uniqueness component.

You might have:

Vlan293 and Vlan294 in VDC 1, Vlan293 and Vlan295 in VDC 2 with Vlan293 being unique to the VDC's themselves. This would result in two Vlan293's on the device, but they are only contained within the VDC.

Thoughts @jeremystretch?

[jeremystretch]

Interfaces simply need to have unique names per device/VM; no way around that, and I think that's a reasonable limitation.

[jeremystretch]

Great work, thanks @DanSheps!