Custom Relationships do not show in dynamic filter forms

[jathanism]

Environment

• Nautobot version (Docker tag too if applicable): 1.5.x
• Python version: n/a
• Database platform, version: demo.nautobot.com
• Middleware(s):

Steps to Reproduce

1. Create relationship with source content type dcim | device and destination ipam | VLAN
2. Go to Device list view and click filter
3. Try to find "VLANs"

Expected Behavior

The "VLANs" field for custom relationships.

Observed Behavior

It does not show and cannot be used as a filter. In fact, no relationships will show in the "advanced" view filter view. Default filter view they show up.

[jathanism]

It appears the issue is here:

nautobot/nautobot/core/utils/requests.py

Line 157 in 1b5d62d

lookup_field = re.sub(r"__\w+", "", lookup_type)

It has to do with the fact that cr filters are named with their destination e.g. cr_device_to_vlans__destination. And they appear to get filtered out incorrectly since it gets split into cr_device_to_vlans (which does not exist on the filter nor inner form fields). I would guess that custom relationships fields need to be excluded from this and other "split" logic.

There is some other logic that appears to be filtering out things with __ in their name as well in the form code:

nautobot/nautobot/core/forms/forms.py

Line 327 in 1b5d62d

if "__" not in name and name != "q"