Object metadata API create one using workspace migration v2 (#13420)

# Introduction
In this PR we create basic transpilation methods and utils to handle
input to flat, entity to flat, object maps to flat. In order to
transpile everything into a common validation that will be implemented
in another PR

## FieldMetadataEntity typing
Added `never | null` to fields that should never be in order to ease
general abstracted method to pass null, as anw it's what is in the
database

## Todo
- ~~Create a feature flag~~
- Integration test for object creation through metadata api + pg col
introspection and snapshoting

packages/twenty-server/src/engine/core-modules/feature-flag/enums/feature-flag-key.enum.ts

@@ -13,4 +13,5 @@ export enum FeatureFlagKey {
   IS_FIELDS_PERMISSIONS_ENABLED = 'IS_FIELDS_PERMISSIONS_ENABLED',
   IS_CORE_VIEW_SYNCING_ENABLED = 'IS_CORE_VIEW_SYNCING_ENABLED',
   IS_TWO_FACTOR_AUTHENTICATION_ENABLED = 'IS_TWO_FACTOR_AUTHENTICATION_ENABLED',
+  IS_WORKSPACE_MIGRATION_V2_ENABLED = 'IS_WORKSPACE_MIGRATION_V2_ENABLED',
 }