[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/workspace-manager/workspace-migration-v2/utils/__tests__/__snapshots__/flat-entity-deleted-created-updated-matrix-dispatcher.util.spec.ts.snap

@@ -21,6 +21,7 @@ exports[`flatEntityDeletedCreatedUpdatedMatrixDispatcher It should detect a crea
         "isUnique": false,
         "kanbanAggregateOperationViewIds": [],
         "label": "flat field metadata label",
+        "mainGroupByFieldMetadataViewIds": [],
         "morphId": null,
         "name": "flatFieldMetadataName",
         "objectMetadataId": "object-metadata-id-1",
@@ -85,6 +86,7 @@ exports[`flatEntityDeletedCreatedUpdatedMatrixDispatcher It should detect a dele
         "isUnique": false,
         "kanbanAggregateOperationViewIds": [],
         "label": "flat field metadata label",
+        "mainGroupByFieldMetadataViewIds": [],
         "morphId": null,
         "name": "flatFieldMetadataName",
         "objectMetadataId": "object-metadata-id-1",
@@ -167,6 +169,7 @@ exports[`flatEntityDeletedCreatedUpdatedMatrixDispatcher It should detect create
         "isUnique": false,
         "kanbanAggregateOperationViewIds": [],
         "label": "flat field metadata label",
+        "mainGroupByFieldMetadataViewIds": [],
         "morphId": null,
         "name": "flatFieldMetadataName",
         "objectMetadataId": "object-metadata-id-1",
@@ -213,6 +216,7 @@ exports[`flatEntityDeletedCreatedUpdatedMatrixDispatcher It should detect create
         "isUnique": false,
         "kanbanAggregateOperationViewIds": [],
         "label": "flat field metadata label",
+        "mainGroupByFieldMetadataViewIds": [],
         "morphId": null,
         "name": "flatFieldMetadataName",
         "objectMetadataId": "object-metadata-id-1",