Add detailed view for devices under contract

[progala]

Environment

• Nautobot version: 1.6.0
• nautobot-plugin-device-lifecycle-mgmt version: 1.3.2

Proposed Functionality

Add "Devices under contract" detailed view that, for a given contract, shows devices with serial number, device name, inventory items, etc. This view should have export functionality generating CSV file that can be used to easily compare contract devices across time.

Use Case

As Nelly, Network Engineer, I want to be able to easily see details of the devices linked to a specific contract. I want to be able to export that data so that I can see what devices are being added/removed from the contract.