Custom Fields cannot filter by name for content_types

[FragmentedPacket]

Environment

• Python version: Python 3.8
• Nautobot version: 1.0.0.b2

Steps to Reproduce

1. Attempt to filter extras/custom-fields by content_types=dcim.device it fails with Observed Behavior below.
2. Attempt to filter extras/statuses by content_types=dcim.device and it works

Expected Behavior

Filter custom fields for any that are tied to dcim.device

Also, should content-types providers an integer instead of UUID. Not sure if this is due to it being a Django construct primarily.

@jmcgill298 @jvanderaa

Observed Behavior

{
  "content_types": [
    "“dcim.device” is not a valid value."
  ]
}

[jathanism]

Thanks @FragmentedPacket for the report.

We won't be able to solve for integer PKs for content types because they are built-in, but we can at least hide them. We just need to revise the custom fields relationship to use the same content-types related field subclass we added to support a cleaner UX for working with statuses.