[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-server/src/engine/metadata-modules/flat-entity/constant/all-metadata-many-to-one-relations.constant.ts

@@ -41,6 +41,10 @@ export const ALL_METADATA_RELATED_METADATA_BY_FOREIGN_KEY = {
       metadataName: 'fieldMetadata',
       flatEntityForeignKeyAggregator: 'calendarViewIds',
     },
+    mainGroupByFieldMetadataId: {
+      metadataName: 'fieldMetadata',
+      flatEntityForeignKeyAggregator: 'mainGroupByFieldMetadataViewIds',
+    },
     objectMetadataId: {
       metadataName: 'objectMetadata',
       flatEntityForeignKeyAggregator: 'viewIds',