[Requires "warm" cache flush (no immediate downtime before flush)] Migrate viewGroup.fieldMetadataId -> view.mainGroupByFieldMetadataId (1/3) (#16206)

In this PR (1/3)
- introduce view.mainGroupByFieldMetadataId as the new reference
determining which fieldMetadataId is used in a grouped view, in order to
deprecate viewGroup.fieldMetadataId which creates inconsistencies.
view.mainGroupByFieldMetadataId is now filled at every view creation,
though not in use yet.
- Introduce a command to backfill view.mainGroupByFieldMetadataId for
existing views + delete all viewGroup.fieldMetadataId with a
fieldMetadataId that is not view.mainGroupByFieldMetadataId. (It should
concern 37 active workspaces)
- Temporarily disable the option to change a grouped view's
fieldMetadataId as for now it creates inconsistencies. This feature can
be reintroduced when we have done the full migration.

In a next PR
- (2/3) use view.mainGroupByFieldMetadataId instead of
viewGroup.fieldMetadataId. In FE we may keep viewGroup.fieldMetadataId
as a state (TBD). View groups will now be created / deleted as a side
effect of view's mainGroupByFieldMetadataId update.
- (3/3) remove viewGroup.fieldMetadataId

---------

Co-authored-by: Charles Bochet <charles@twenty.com>

packages/twenty-front/src/modules/object-record/object-options-dropdown/components/ObjectOptionsDropdownRecordGroupsContent.tsx

@@ -113,13 +113,10 @@ export const ObjectOptionsDropdownRecordGroupsContent = () => {
         >
           {currentView?.key !== 'INDEX' && (
             <>
-              <SelectableListItem
-                itemId="GroupBy"
-                onEnter={() => onContentChange('recordGroupFields')}
-              >
+              <SelectableListItem itemId="GroupBy">
                 <MenuItem
                   focused={selectedItemId === 'GroupBy'}
-                  onClick={() => onContentChange('recordGroupFields')}
+                  disabled
                   LeftIcon={IconLayoutList}
                   text={t`Group by`}
                   contextualText={recordGroupFieldMetadata?.label}