Unable to create custom field of type object or multiobject via API

[squintfox]

NetBox version

v3.2-beta2

Python version

3.9

Steps to Reproduce

1. POST the following to: https:///api/extras/custom-fields/
   {
   "content_types": [
   "ipam.prefix"
   ],
   "type": "object",
   "data_type": "object",
   "object_type": "circuits.circuit",
   "name": "circuit",
   "label": "Circuit"
   }

Expected Behavior

A new custom field should be created.

Observed Behavior

The API returns:
{
"object_type": [
"Object fields must define an object type."
]
}

It does not matter what value you supply for object_type or if you don't specify one at all.

[squintfox]

I believe (at least in part) the issue is the the field object_type is missing from CustomFieldSerializer in /netbox/netbox/extras/api/serializers.py. I modified this:

fields = [
'id', 'url', 'display', 'content_types', 'type', 'data_type', 'name', 'label', 'description', 'required',
'filter_logic', 'default', 'weight', 'validation_minimum', 'validation_maximum', 'validation_regex',
'object_type', 'choices', 'created', 'last_updated',
]

After I restarted netbox, object_type was now shown in API GET queries for custom fields (it was not previously) and I was able to create a custom field by supplying the int id of "circuits.circuit". Given what I've see of the API and how it handles linked objects, this doesn't seem like a complete solution, but hopefully this is helpful for someone who understands it better than I do.

[jeremystretch]

@squintfox yep, that's pretty much it. In this case, we want to make object_type a ContentTypeField, so that it returns a human-friendly descriptor (e.g. "circuit.circuit") instead of the PK, adding the missing field was the key. Thanks for the report!