feat(front): allow advanced relation fields in FieldWidget selector (#22005)

## After

<img width="706" height="760" alt="image"
src="https://github.com/user-attachments/assets/d118285f-baab-4187-988c-d0180d61a629"
/>
<img width="707" height="372" alt="image"
src="https://github.com/user-attachments/assets/5676d829-2ec1-494e-a8f0-5998f1f0c3c8"
/>


## Summary

The FieldWidget field-selection dropdown currently filters out relation
fields whose target is a system object, so users can't pick fields like
`calendarEventParticipants` on the CalendarEvent record page. The widget
itself can render them just fine as boxed relations — the restriction
only lives in the picker.

This unblocks the consistency story from #22003 (revert of #21857): once
shipped, participants can be added to the calendar event record page via
the existing FieldWidget mechanism instead of a bespoke side-panel page.

## Changes

- `isFieldCellSupported`: adds an opt-in `includeSystemObjectRelations`
option that skips the `isObjectMetadataAvailableForRelation` system
check.
- `useFieldListFieldMetadataItems`: forwards the option through to
`isFieldCellSupported`. Default is `false`, so all existing callers keep
current behavior.
- `useFieldWidgetEligibleFields`: turns the option on, so the
FieldWidget selector now surfaces fields like
`calendarEventParticipants`, `messageParticipants`, etc.

## Test plan

- [x] `nx typecheck twenty-front`
- [x] `nx lint:diff-with-main twenty-front`
- [ ] CI
- [ ] Manually verify the FieldWidget dropdown now lists
`calendarEventParticipants` on a CalendarEvent record page, and that
selecting it renders a participants list via the existing relation
card/field widget.

https://claude.ai/code/session_01RnMcjL35wdCRzpXN257RLJ

---
_Generated by [Claude
Code](https://claude.ai/code/session_01RnMcjL35wdCRzpXN257RLJ)_

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packages/twenty-front/src/modules/object-record/utils/isAdvancedRelationFieldMetadataItem.ts

@@ -0,0 +1,12 @@
+import { type EnrichedObjectMetadataItem } from '@/object-metadata/types/EnrichedObjectMetadataItem';
+import { type FieldMetadataItem } from '@/object-metadata/types/FieldMetadataItem';
+import { isFieldCellSupported } from '@/object-record/utils/isFieldCellSupported';
+
+export const isAdvancedRelationFieldMetadataItem = (
+  fieldMetadataItem: FieldMetadataItem,
+  objectMetadataItems: EnrichedObjectMetadataItem[],
+) =>
+  !isFieldCellSupported(fieldMetadataItem, objectMetadataItems) &&
+  isFieldCellSupported(fieldMetadataItem, objectMetadataItems, {
+    includeSystemObjectRelations: true,
+  });

packages/twenty-front/src/modules/object-record/utils/isFieldCellSupported.ts

@@ -5,9 +5,14 @@ import { isHiddenSystemField } from '@/object-metadata/utils/isHiddenSystemField
 import { isObjectMetadataAvailableForRelation } from '@/object-metadata/utils/isObjectMetadataAvailableForRelation';
 import { FieldMetadataType } from '~/generated-metadata/graphql';
 
+type IsFieldCellSupportedOptions = {
+  includeSystemObjectRelations?: boolean;
+};
+
 export const isFieldCellSupported = (
   fieldMetadataItem: FieldMetadataItem,
   objectMetadataItems: EnrichedObjectMetadataItem[],
+  options: IsFieldCellSupportedOptions = {},
 ) => {
   if (fieldMetadataItem.type === FieldMetadataType.POSITION) {
     return false;
@@ -40,9 +45,12 @@ export const isFieldCellSupported = (
       return true;
     }
 
+    if (!fieldMetadataItem.relation || !relationObjectMetadataItem) {
+      return false;
+    }
+
     if (
-      !fieldMetadataItem.relation ||
-      !relationObjectMetadataItem ||
+      !options.includeSystemObjectRelations &&
       !isObjectMetadataAvailableForRelation(relationObjectMetadataItem)
     ) {
       return false;