Deprecate ObjectMetadataInterface and improve entity typing (#13310)

# Introduction
Following `FieldMetadataInterface` deprecation in
https://github.com/twentyhq/twenty/pull/13264
As for the previous PR will rename and remove all the file in a
secondary PR to avoid conflicts and over loading this one

## Improvements
Removed optional properties from the `objectMetadataEntity` model and
added utils to retrieve test data

## Notes
By touching to `ObjectMetadataDTO` I would have expected a twenty-front
codegenerated types mutation, but it does not seem to be granular enough
to null/undefined coercion

packages/twenty-server/src/engine/core-modules/open-api/utils/components.utils.ts

@@ -142,7 +142,7 @@ const computeSchemaComponent = ({
 
   const result: OpenAPIV3_1.SchemaObject = {
     type: 'object',
-    description: item.description,
+    description: item.description ?? undefined,
     properties: convertObjectMetadataToSchemaProperties({
       item,
       forResponse,