Fix i18n issues on datamodel translation (#13710)

As per title, I believe calling i18n is bad because it's a singleton.

This singleton is being set back and force by users in
i18n.middleware.ts

Strategy:
we need to load the translations dynamically! Should be straight
forward:
- singleton (i18nService) containing all translationMessages
- singleton also containing a map of i18n instances loaded for each
locale => I've checked it's not heavy on RAM at all
- some methods to get the translation for a messageId x locale or the
whole i18n instance

==> use it everywhere, this PR only takes care of data model translation

packages/twenty-server/src/engine/core-modules/i18n/i18n.middleware.ts

@@ -4,6 +4,7 @@ import { i18n } from '@lingui/core';
 import { NextFunction, Request, Response } from 'express';
 import { APP_LOCALES, SOURCE_LOCALE } from 'twenty-shared/translations';
 
+// TODO: this should be deprecated as singleton pattern won't work: user will keep changing locales for eachothers
 @Injectable()
 export class I18nMiddleware implements NestMiddleware {
   use(req: Request, res: Response, next: NextFunction) {

packages/twenty-server/src/engine/core-modules/i18n/i18n.service.ts

@@ -1,6 +1,6 @@
 import { Injectable, OnModuleInit } from '@nestjs/common';
 
-import { i18n } from '@lingui/core';
+import { I18n, MessageOptions, Messages, i18n, setupI18n } from '@lingui/core';
 import { APP_LOCALES, SOURCE_LOCALE } from 'twenty-shared/translations';
 
 import { messages as afMessages } from 'src/engine/core-modules/i18n/locales/generated/af-ZA';
@@ -37,9 +37,11 @@ import { messages as zhHantMessages } from 'src/engine/core-modules/i18n/locales
 
 @Injectable()
 export class I18nService implements OnModuleInit {
+  private i18nInstancesMap: Record<keyof typeof APP_LOCALES, I18n> =
+    {} as Record<keyof typeof APP_LOCALES, I18n>;
+
   async loadTranslations() {
-    // eslint-disable-next-line @typescript-eslint/no-explicit-any
-    const messages: Record<keyof typeof APP_LOCALES, any> = {
+    const messagesByLocale: Record<keyof typeof APP_LOCALES, Messages> = {
       en: enMessages,
       'pseudo-en': pseudoEnMessages,
       'af-ZA': afMessages,
@@ -73,16 +75,45 @@ export class I18nService implements OnModuleInit {
       'zh-TW': zhHantMessages,
     };
 
-    // eslint-disable-next-line @typescript-eslint/no-explicit-any
-    (Object.entries(messages) as [keyof typeof APP_LOCALES, any][]).forEach(
-      ([locale, message]) => {
-        i18n.load(locale, message);
-      },
-    );
+    (
+      Object.entries(messagesByLocale) as [keyof typeof APP_LOCALES, Messages][]
+    ).forEach(([locale, messages]) => {
+      const localeI18n = setupI18n();
 
+      localeI18n.load(locale, messages);
+      localeI18n.activate(locale);
+
+      this.i18nInstancesMap[locale] = localeI18n;
+
+      // TODO: deprecate this line which is legacy as soon as we only use the i18nInstancesMap
+      // Also deprecate i18n.middleware.ts
+      i18n.load(locale, messages);
+    });
+
+    // TODO: deprecate this line which is legacy as soon as we only use the i18nInstancesMap
     i18n.activate(SOURCE_LOCALE);
   }
 
+  getI18nInstance(locale: keyof typeof APP_LOCALES) {
+    return this.i18nInstancesMap[locale];
+  }
+
+  translateMessage({
+    messageId,
+    values,
+    locale = SOURCE_LOCALE,
+    options,
+  }: {
+    messageId: string;
+    values?: Record<string, string>;
+    locale?: keyof typeof APP_LOCALES;
+    options?: MessageOptions;
+  }) {
+    const i18n = this.getI18nInstance(locale);
+
+    return i18n._(messageId, values, options);
+  }
+
   async onModuleInit() {
     this.loadTranslations();
   }