Add support for Multi-member devices

[dgarros]

Environment

• Python version: 3.7.7
• NetBox version: 2.8.7
• ntc-netbox-plugin-onboarding version: 1.2.0

Proposed Functionality

Add support for multi-member devices like Cisco Stackwise or Juniper Virtual Chassis. (1 logicial device, 1 configuration, multiple physical devices)
When a device composed of multiple members is getting onboarded, each member should be created in NetBox with its own serial number and all members should be part of a Virtual Chassis Object with the appropriate number id.

The name of the primary device in the stack/vc should be the hostname of the device and the other members should have a name derived from the hostname:

• Hostname: stackA
• Primary device name: stackA
• other_member: stackA:{memberid}

There are other similar devices that would be great to support in the future like Cisco VSS

If a multi member device with the same hostname already exist, each member should be updated to reflect the current status of the device: serial number, member id, new member, missing member etc ...

Use Case

The use case for this feature is to simplify the onboarding of multi member devices and provide a framework to support vendor specific code.