[FlexibleSchema] Add IndexMetadata decorator (#5981)

## Context
Our Flexible Schema engine dynamically generates entities/tables/APIs
for us but was not flexible enough to build indexes in the DB. With more
and more features involving heavy queries such as Messaging, we are now
adding a new WorkspaceIndex() decorator for our standard objects (will
come later for custom objects). This decorator will give enough
information to the workspace sync metadata manager to generate the
proper migrations that will create or drop indexes on demand.
To be aligned with the rest of the engine, we are adding 2 new tables:
IndexMetadata and IndexFieldMetadata, that will store the info of our
indexes.

## Implementation

```typescript
@WorkspaceEntity({
  standardId: STANDARD_OBJECT_IDS.person,
  namePlural: 'people',
  labelSingular: 'Person',
  labelPlural: 'People',
  description: 'A person',
  icon: 'IconUser',
})
export class PersonWorkspaceEntity extends BaseWorkspaceEntity {
  @WorkspaceField({
    standardId: PERSON_STANDARD_FIELD_IDS.email,
    type: FieldMetadataType.EMAIL,
    label: 'Email',
    description: 'Contact’s Email',
    icon: 'IconMail',
  })
  @WorkspaceIndex()
  email: string;
```
By simply adding the WorkspaceIndex decorator, sync-metadata command
will create a new index for that column.
We can also add composite indexes, note that the order is important for
PSQL.
```typescript
@WorkspaceEntity({
  standardId: STANDARD_OBJECT_IDS.person,
  namePlural: 'people',
  labelSingular: 'Person',
  labelPlural: 'People',
  description: 'A person',
  icon: 'IconUser',
})
@WorkspaceIndex(['phone', 'email'])
export class PersonWorkspaceEntity extends BaseWorkspaceEntity {
```

Currently composite fields and relation fields are not handled by
@WorkspaceIndex() and you will need to use this notation instead
```typescript
@WorkspaceIndex(['companyId', 'nameFirstName'])
export class PersonWorkspaceEntity extends BaseWorkspaceEntity {
```
<img width="700" alt="Screenshot 2024-06-21 at 15 15 45"
src="https://github.com/twentyhq/twenty/assets/1834158/ac6da1d9-d315-40a4-9ba6-6ab9ae4709d4">

Next step: We might need to implement more complex index expressions,
this is why we have an expression column in IndexMetadata.
What I had in mind for the decorator, still open to discussion
```typescript
@WorkspaceIndex(['nameFirstName', 'nameLastName'], { expression: "$1 || ' ' || $2"})
export class PersonWorkspaceEntity extends BaseWorkspaceEntity {
```

---------

Co-authored-by: Charles Bochet <charles@twenty.com>

packages/twenty-server/src/database/typeorm/metadata/migrations/1718985664968-addIndexMetadataTable.ts

@@ -0,0 +1,28 @@
+import { MigrationInterface, QueryRunner } from 'typeorm';
+
+export class AddIndexMetadataTable1718985664968 implements MigrationInterface {
+  name = 'AddIndexMetadataTable1718985664968';
+
+  public async up(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(
+      `CREATE TABLE "metadata"."indexMetadata" ("id" uuid NOT NULL DEFAULT uuid_generate_v4(), "name" character varying NOT NULL, "workspaceId" character varying, "objectMetadataId" uuid NOT NULL, CONSTRAINT "PK_f73bb3c3678aee204e341f0ca4e" PRIMARY KEY ("id"))`,
+    );
+    await queryRunner.query(
+      `CREATE TABLE "metadata"."indexFieldMetadata" ("id" uuid NOT NULL DEFAULT uuid_generate_v4(), "indexMetadataId" uuid NOT NULL, "fieldMetadataId" uuid NOT NULL, "order" integer NOT NULL, CONSTRAINT "PK_5928f67e43eff7d95aa79fd96fd" PRIMARY KEY ("id"))`,
+    );
+    await queryRunner.query(
+      `ALTER TABLE "metadata"."indexMetadata" ADD CONSTRAINT "FK_051487e9b745cb175950130b63f" FOREIGN KEY ("objectMetadataId") REFERENCES "metadata"."objectMetadata"("id") ON DELETE CASCADE ON UPDATE NO ACTION`,
+    );
+    await queryRunner.query(
+      `ALTER TABLE "metadata"."indexFieldMetadata" ADD CONSTRAINT "FK_b20192c432612eb710801dd5664" FOREIGN KEY ("indexMetadataId") REFERENCES "metadata"."indexMetadata"("id") ON DELETE CASCADE ON UPDATE NO ACTION`,
+    );
+    await queryRunner.query(
+      `ALTER TABLE "metadata"."indexFieldMetadata" ADD CONSTRAINT "FK_be0950612a54b58c72bd62d629e" FOREIGN KEY ("fieldMetadataId") REFERENCES "metadata"."fieldMetadata"("id") ON DELETE CASCADE ON UPDATE NO ACTION`,
+    );
+  }
+
+  public async down(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(`DROP TABLE "metadata"."indexFieldMetadata"`);
+    await queryRunner.query(`DROP TABLE "metadata"."indexMetadata"`);
+  }
+}