common api - null equivalence (#15926)

closes https://github.com/twentyhq/core-team-issues/issues/1629

To do before requesting review : 
- filter update

Migration to come in an other PR


Strat : 
1/  Null transformation

- [x] Transform NULL equivalent value to NULL in field validation in
common api - pre-query - with feature flag
- [ ] Same logic in ORM (Not done, complex to handle feature flag here)
- [x] Transform NULL value to equivalent in data formatting in ORM -
post-query

2/ Migration (in other PR) for fieldMetadata not nullable with default
defaultValue (empty string, ...)

- [ ] Remove NOT NULL db constraint
- [ ] Update record value to NULL
- [ ] Update field metadata : isNullable:true
- [ ] Update uniqueIndex whereClause (also for standard uniqueIndex) 
- [ ] Activate feature flag

3/ Update metadata creation

- [x] No more default default value
- [x] Update standard field nullability
- [x] Remove index default whereClause for standard field

4/ Update filter

- [x] When filtering on NULL or empty string, be sure all records are
returned (the one with NULL + the one with "")

5/ Test

- [ ] Strat. to do

packages/twenty-server/src/engine/core-modules/feature-flag/enums/feature-flag-key.enum.ts

@@ -16,4 +16,5 @@ export enum FeatureFlagKey {
   IS_WORKFLOW_RUN_STOPPAGE_ENABLED = 'IS_WORKFLOW_RUN_STOPPAGE_ENABLED',
   IS_DASHBOARD_V2_ENABLED = 'IS_DASHBOARD_V2_ENABLED',
   IS_GLOBAL_WORKSPACE_DATASOURCE_ENABLED = 'IS_GLOBAL_WORKSPACE_DATASOURCE_ENABLED',
+  IS_NULL_EQUIVALENCE_ENABLED = 'IS_NULL_EQUIVALENCE_ENABLED',
 }

packages/twenty-server/src/engine/core-modules/record-crud/services/upsert-record.service.ts

@@ -128,11 +128,13 @@ export class UpsertRecordService {
           ? conflictPathsUniqueFieldsToUpdate
           : ['id'];
 
+      //TODO : To delete once IS_NULL_EQUIVALENCE_ENABLED feature flag removed
       const indexPredicate = uniqueFieldsToUpdate
         .map((field) =>
           computeUniqueIndexWhereClause({
             type: field.type,
             name: field.name,
+            defaultValue: field.defaultValue,
           }),
         )
         .filter(isDefined);

packages/twenty-server/src/engine/core-modules/record-transformer/utils/transform-emails-value.util.ts

@@ -1,15 +1,21 @@
 import { isNonEmptyString } from '@sniptt/guards';
 
-// eslint-disable-next-line @typescript-eslint/no-explicit-any
-export const transformEmailsValue = (value: any): any => {
+export const transformEmailsValue = (
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  value: any,
+  isNullEquivalenceEnabled: boolean = false,
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+): any => {
   if (!value) {
     return value;
   }
 
-  let additionalEmails = value?.additionalEmails;
+  let additionalEmails: string | null = value?.additionalEmails;
   const primaryEmail = value?.primaryEmail
     ? value.primaryEmail.toLowerCase()
-    : '';
+    : isNullEquivalenceEnabled
+      ? null
+      : '';
 
   if (additionalEmails) {
     try {
@@ -22,6 +28,13 @@ export const transformEmailsValue = (value: any): any => {
       additionalEmails = JSON.stringify(
         emailArray.map((email) => email.toLowerCase()),
       );
+
+      if (isNullEquivalenceEnabled) {
+        additionalEmails =
+          Array.isArray(emailArray) && emailArray.length === 0
+            ? null
+            : additionalEmails;
+      }
     } catch {
       /* empty */
     }

packages/twenty-server/src/engine/core-modules/record-transformer/utils/transform-links-value.util.ts

@@ -1,11 +1,11 @@
 import { isNonEmptyString } from '@sniptt/guards';
 import isEmpty from 'lodash.isempty';
+import { type LinkMetadataNullable } from 'twenty-shared/types';
 import {
   isDefined,
   lowercaseUrlOriginAndRemoveTrailingSlash,
   parseJson,
 } from 'twenty-shared/utils';
-import { type LinkMetadataNullable } from 'twenty-shared/types';
 
 import { removeEmptyLinks } from 'src/engine/core-modules/record-transformer/utils/remove-empty-links';
 

packages/twenty-server/src/engine/core-modules/record-transformer/utils/transform-phones-value.util.ts

@@ -5,6 +5,10 @@ import {
   parsePhoneNumberWithError,
 } from 'libphonenumber-js';
 import isEmpty from 'lodash.isempty';
+import {
+  type AdditionalPhoneMetadata,
+  type PhonesMetadata,
+} from 'twenty-shared/types';
 import {
   getCountryCodesForCallingCode,
   isDefined,
@@ -12,10 +16,6 @@ import {
   parseJson,
   removeUndefinedFields,
 } from 'twenty-shared/utils';
-import {
-  type AdditionalPhoneMetadata,
-  type PhonesMetadata,
-} from 'twenty-shared/types';
 
 import {
   RecordTransformerException,