WebHook should provide old data together with new data

[matt852]

Environment

• Python version: 3.6.8
• Nautobot version: 1.0.0b3

Proposed Functionality

I'm submitting this feature request on behalf of @itdependsnetworks for webhooks to include old and new data (pre/post changes). There was an active issue with Netbox for this same issue, where the feature was recently merged in. It may be possible to reference this issue/PR and replicate the functionality in Nautobot.

netbox-community/netbox#3451
netbox-community/netbox@c6641ec

Use Case

An example use case from the linked issue above:
User creates Device/VM in Nautobot and assigns IP address with DNS Name --> DNS Name gets written into the DNS Server. User changes the DNS Name, old DNS Name gets deleted in the DNS and the new one created.

Database Changes

No

External Dependencies

None

[jedelman8]

@glennmatthews does this need to be a breaking change? Can we only add a new key-value pair with the original/old data so receiving systems don't break? If so, we can move back to near-term.

[glennmatthews]

Looking at the NetBox implementation, it was done as a new parallel set of key-value pairs, so if we follow that pattern, it should be reasonable.

[bryanculver]

Merged into next.