Field metadata v2 relation (#13562)

# Introduction
- deferrable constraint on foreignKey definition
- fix relation creation input transpilation to flat field metadata
- fix validation to allow contextual validation on not already created
field metadata ( usefull for relation, and will be necessary for the
import )

packages/twenty-server/src/database/typeorm/core/migrations/common/1752993324991-makeFieldMetadataRelationConstraintDeferrable.ts

@@ -0,0 +1,31 @@
+import { MigrationInterface, QueryRunner } from 'typeorm';
+
+export class MakeFieldMetadataRelationConstraintDeferrable1752993324991
+  implements MigrationInterface
+{
+  name = 'MakeFieldMetadataRelationConstraintDeferrable1752993324991';
+
+  public async up(queryRunner: QueryRunner): Promise<void> {
+    // Drop the existing constraint
+    await queryRunner.query(
+      `ALTER TABLE "core"."fieldMetadata" DROP CONSTRAINT "FK_47a6c57e1652b6475f8248cff78"`,
+    );
+
+    // Recreate it as deferrable and initially deferred
+    await queryRunner.query(
+      `ALTER TABLE "core"."fieldMetadata" ADD CONSTRAINT "FK_47a6c57e1652b6475f8248cff78" FOREIGN KEY ("relationTargetFieldMetadataId") REFERENCES "core"."fieldMetadata"("id") DEFERRABLE INITIALLY DEFERRED`,
+    );
+  }
+
+  public async down(queryRunner: QueryRunner): Promise<void> {
+    // Drop the deferrable constraint
+    await queryRunner.query(
+      `ALTER TABLE "core"."fieldMetadata" DROP CONSTRAINT "FK_47a6c57e1652b6475f8248cff78"`,
+    );
+
+    // Recreate it as non-deferrable
+    await queryRunner.query(
+      `ALTER TABLE "core"."fieldMetadata" ADD CONSTRAINT "FK_47a6c57e1652b6475f8248cff78" FOREIGN KEY ("relationTargetFieldMetadataId") REFERENCES "core"."fieldMetadata"("id")`,
+    );
+  }
+}