feat: manually implement joinColumn (#6022)

This PR introduce a new decorator named `@WorkspaceJoinColumn`, the goal
of this one is to manually declare the join columns inside the workspace
entities, so we don't have to rely on `ObjectRecord` type.

This decorator can be used that way:

```typescript
  @WorkspaceRelation({
    standardId: ACTIVITY_TARGET_STANDARD_FIELD_IDS.company,
    type: RelationMetadataType.MANY_TO_ONE,
    label: 'Company',
    description: 'ActivityTarget company',
    icon: 'IconBuildingSkyscraper',
    inverseSideTarget: () => CompanyWorkspaceEntity,
    inverseSideFieldKey: 'activityTargets',
  })
  @WorkspaceIsNullable()
  company: Relation<CompanyWorkspaceEntity> | null;

  // The argument is the name of the relation above
  @WorkspaceJoinColumn('company')
  companyId: string | null;
```

packages/twenty-server/src/utils/typed-reflect.ts

@@ -8,7 +8,6 @@ export interface ReflectMetadataTypeMap {
   ['workspace:is-system-metadata-args']: true;
   ['workspace:is-audit-logged-metadata-args']: false;
   ['workspace:is-primary-field-metadata-args']: true;
-  ['workspace:join-column']: true;
 }
 
 export class TypedReflect {