Add integration tests for /metadata + fix relation deletion (#8706)

In this PR

1. Add integration tests for /metadata (master issue:
https://github.com/twentyhq/twenty/issues/8719)
2. Fix relation deletion: index on "from" object was not deleted,
impeding creation of a new relation between the same two objects A and B
after relation between A and B was deleted

packages/twenty-server/test/integration/metadata/suites/utils/make-metadata-api-request.util.ts

@@ -0,0 +1,19 @@
+import { ASTNode, print } from 'graphql';
+import request from 'supertest';
+
+type GraphqlOperation = {
+  query: ASTNode;
+  variables?: Record<string, unknown>;
+};
+
+export const makeMetadataAPIRequest = (graphqlOperation: GraphqlOperation) => {
+  const client = request(`http://localhost:${APP_PORT}`);
+
+  return client
+    .post('/metadata')
+    .set('Authorization', `Bearer ${ACCESS_TOKEN}`)
+    .send({
+      query: print(graphqlOperation.query),
+      variables: graphqlOperation.variables || {},
+    });
+};