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/database/typeorm/core/migrations/common/1764672601466-change-agent-description-to-text.ts

@@ -0,0 +1,19 @@
+import { type MigrationInterface, type QueryRunner } from 'typeorm';
+
+export class ChangeAgentDescriptionToText1764672601466
+  implements MigrationInterface
+{
+  name = 'ChangeAgentDescriptionToText1764672601466';
+
+  public async up(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(
+      `ALTER TABLE "core"."agent" ALTER COLUMN "description" TYPE text`,
+    );
+  }
+
+  public async down(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(
+      `ALTER TABLE "core"."agent" ALTER COLUMN "description" TYPE character varying`,
+    );
+  }
+}