Migrate agent v2 (#16214)

# Introduction
Closes https://github.com/twentyhq/core-team-issues/issues/1980

In this PR we migrate the agent from v1 to v2.

## New FlatRoleTargetByAgentIdMaps
Derivated the `flatRoleTargetMaps` to be building a
`flatRoleTargetByAgentIdMaps` to ease retrieving a roleId to associate
to an agent

## Coverage
Added strong coverage on both failing and successful CRU agents
operations

---------

Co-authored-by: Weiko <corentin@twenty.com>

packages/twenty-server/src/engine/workspace-cache/utils/regroup-entities-by-related-entity-id.ts

@@ -0,0 +1,39 @@
+import { isDefined } from 'class-validator';
+import { type AllMetadataName } from 'twenty-shared/metadata';
+
+import { type MetadataEntity } from 'src/engine/metadata-modules/flat-entity/types/metadata-entity.type';
+import { type MetadataManyToOneJoinColumn } from 'src/engine/metadata-modules/flat-entity/types/metadata-many-to-one-join-column.type';
+
+export type RegroupEntitiesByRelatedEntityIdArgs<T extends AllMetadataName> =
+  MetadataManyToOneJoinColumn<T> extends never
+    ? never
+    : {
+        entities: MetadataEntity<T>[];
+        foreignKey: MetadataManyToOneJoinColumn<T>;
+      };
+export const regroupEntitiesByRelatedEntityId = <T extends AllMetadataName>({
+  entities,
+  foreignKey,
+}: RegroupEntitiesByRelatedEntityIdArgs<T>) => {
+  const entitiesByRelatedEntityId = new Map<string, { id: string }[]>();
+
+  for (const entity of entities) {
+    const currentRelatedEntityId = entity[
+      foreignKey as keyof MetadataEntity<T>
+    ] as string;
+
+    if (!isDefined(currentRelatedEntityId)) {
+      continue;
+    }
+
+    if (!entitiesByRelatedEntityId.has(currentRelatedEntityId)) {
+      entitiesByRelatedEntityId.set(currentRelatedEntityId, []);
+    }
+
+    entitiesByRelatedEntityId
+      .get(currentRelatedEntityId)!
+      .push({ id: entity.id });
+  }
+
+  return entitiesByRelatedEntityId;
+};